You sound like a man badly in need of a Clymer's maintenance manual, or Suzuki service manual...

The down and dirty:

1. Turn your handlebars until the front brake master cylinder on the right side of your handlebars is LEVEL. (You may have to loosen the bracket which attaches the master cylinder to the bars to get it really level.)

2. Now look at the fluid level in the reservoir through the little sight glass on the front side. If the level is low, remove the top of the reservoir and add just enough DOT type 3 or 4 brake fluid to bring it up to the "full" mark on the outside by the sight glass.

3. Put the top back on the reservoir, reposition the brake lever/reservoir to a comfortable riding position and tighten it down.

Good to go!  

If the fluid level is low & you dont have a leak, you may need pads.
If the reservoir is allowed to lose prime, getting it back can be a bit of a hassle, tho there are numerous ways to get it pumping again.

At least on my '07, the brake fluid reservoir cover has an engraved label telling you what sort of fluid to use. It says DOT 4. The information isn't too hard to find - it is right on top.

Copied from http://www.tccoa.com/brake-fluid/

DOT3
    DOT3 brake fluid is the "conventional" brake fluid used in most vehicles.

   Advantages:
         DOT3 fluid is inexpensive, and available at most gas stations, department stores, and any auto parts store.

   Disadvantages:
         DOT3 fluid eats paint!
         DOT3 fluid absorbs water very readily. (This is often referred to as being hydroscopic.) As such, once a container of DOT3 has been opened, it should not be stored for periods much longer than a week before use.
         Since DOT3 fluid absorbs water, any moisture absorbed by the fluid can encourage corrosion in the brake lines and cylinders.

DOT4
    DOT4 brake fluid is the brake fluid suggested for use in some late model cars.

    Advantages:
         DOT4 fluid is available at most auto parts stores, and at some (but not all) gas stations or department stores.
         DOT4 fluid does not absorb water as readily as DOT3 fluid.
         DOT4 fluid has a higher boiling point than DOT3 fluid, making it more suitable for high performance applications where the brake systems are expected to get hot.

    Disadvantages:
         DOT4 fluid eats paint! Small leaks around the master cylinder will eventually dissolve away the paint on your bodywork in the general vicinity of the leak, and then give rust a chance to attack the body of your car!
         DOT4 fluid is generally about 50% more expensive than DOT3 fluid.
         Since DOT4 fluid still absorbs some water, any moisture absorbed by the fluid can encourage corrosion in the brake lines and cylinders.

DOT5
    DOT5 brake fluid is also known as "silicone" brake fluid.

    Advantages:
         DOT5 doesn't eat paint.
         DOT5 does not absorb water and may be useful where water absorption is a problem.
         DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.)

    Disadvantages:
         DOT5 does NOT mix with DOT3, DOT4 or DOT5.1. Most reported problems with DOT5 are probably due to some
         degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic
         system.
         Reports of DOT5 causing premature failure of rubber brake parts were more common with early DOT5
         formulations. This is thought to be due to improper addition of swelling agents and has been fixed in recent
         formulations.
         Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can
         cause localized corrosion in the hydraulics.
         Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form
         large bubbles over time. It may be necessary to do a series of bleeds.
         DOT5 is slightly compressible (giving a very slightly soft pedal), and has a lower boiling point than DOT4.
         DOT5 is about twice as expensive as DOT4 fluid. It is also difficult to find, generally only available at selected
         auto parts stores.

DOT5.1
          DOT5.1 is a relatively new brake fluid that is causing no end of confusion amongst mechanics. The DOT could avoid a
          lot of confusion by giving this new fluid a different designation. The 5.1 designation could lead one to believe that it's a
          modification of silicone-based DOT 5 brake fluid. Calling it 4.1 or 6 might have been more appropriate since it's a
          glycol-based fluid like the DOT 3 and 4 types, not silicone-based like DOT 5 fluid.

          As far as the basic behavior of 5.1 fluids, they are much like "high performance" DOT4 fluids, rather than traditional
          DOT5 brake fluids.

    Advantages:
         DOT5.1 provides superior performance over the other brake fluids discussed here. It has a higher boiling point,
         either dry or wet, than DOT 3 or 4. In fact, its dry boiling point (about 275 degrees C) is almost as high as racing
         fluid (about 300 degrees C) and 5.1's wet boiling point (about 175 to 200 degrees C) is naturally much higher
         than racing's (about 145 C).
         DOT5.1 is said to be compatible with all rubber formulations.

    Disadvantages:
         DOT5.1 fluids (and Spectro's Supreme DOT4) are non-silicone fluids and will absorb water.
         DOT5.1 fluids, like DOT3 & DOT4 will eat paint.
         DOT 5.1 fluids are difficult to find for sale, typically at very few auto parts stores, mostly limited to "speed shops."
         DOT 5.1 will be more expensive than DOT3 or DOT4, and more difficult to find.

DOT 4 is listed in the '02 owners manual
DOT 4 is listed on the '02 master cylinder cap
'86-'94 Clymer lists DOT 3 or 4
SSM circa '86 lists DOT 3 or 4

DOT 4 is slightly better fluid, but I wouldn't go nuts over it.

Use of DOT 3 is acceptable with a higher maintenance level.

Brake fluid is cheap and easy to replace, do it yearly.

How easy?
Level out the master cyl as mentioned before
take cap off
put a tube on the brake bleeder nipple and place it in the bottom of a 6oz jar
open bleeder
fluid will flow by itself
when the fluid gets about 1/3 high, refill and maintain.
when the 6oz jar is filled you're done
close bleeder
refill master to fill line and cap

repeat next year and every time you change pads.

Coupl'a points about brake fluid:

• Use any new, fresh, tightly sealed brake fluid except DOT5 silicone.  A DOT4 fluid is the best choice.

• DOT3 is a polyglycol ether compound.  DOT4, 4+, and 5.1 have borates and other minor chemical changes to give them their improved heat resistance.

• All brake fluid is synthetic.  Don't fall for any label hype.  There is nothing natural about polyglycol ether or silicone.

• The Department of Transportation issues performance regulations, not chemical composition regulations.  DOT5 meets certain performance specs.  In the past those specs were only met using a silicone fluid.  In recent years the specs were met using conventional chemistry and the fluids got named DOT4+ or DOT5.1, the same performance and not official names, as a way to show that they equal DOT5 performance without silicone chemistry.

Don't forget to change the brake fluid in the family fleet, cars and trucks, periodically.  Dumping the moisture contaminated fluid will extend the life of the calipers.  In the heat of emergency braking the moisture will flash to steam, the brake pedal or lever goes all the way down, and the vehicle does not stop.  If the vehicle is stopped, the telltale is that the brakes work normally after things cool, but the fluid absolutely must be changed.  I know of two fatality wrecks locally caused by overheated brake fluid, and have a friend who got his truck and horse trailer stopped using the parking brake and downshifting without a wreck with exactly these symptoms.  By the way, the heat of extended emergency braking, even if the rig stops OK, can cause changes to the brake fluid, and the fluid must be changed as well as the pads or shoes checked for glazing from overheating.  Convince drivers you know that the safe way to retard their speed on long downgrades is by downshifting so the rig almost holds the speed they feel is safe, and then they just use intermittent moderate braking for precise speed control.  Motorcycles are somewhat different due to rear tire traction issues, but bikes, especially when heavily laden, still need to avoid overheated brakes on long downgrades.

Dot 3 is fit for all...

But if I were a heavy user I'd want Dot 4+

Anybody turn their disk blue lately?
Yes you mr. dragon rider, 2up no less.
You better have the gooood stuff.