Since the OP, helmkev, is new, I'll add a few comments about cutters.
When you first engage the PTO, use a low RPM and keep your hand or foot near the throttle (so you can increase RPM if the tractor starts to stall). Do NOT run it up to PTO RPM and engage. An easy start lessens the shock to both the tractor and implement.
You'll feel some vibration (may be heavy, initially) and hear a "Bang". The cutter's blades pivot, so the cutter will not be balanced until they extend (that's the "Bang").
Once the vibration eases up, increase the RPM to PTO speed (should be a mark on your tachometer) and start mowing.
I leave my loader on with the bucket low. Depending on the density of the brush, you may not see obstructions. The low bucket is your "early warning system". Unless you are very very familar with the area you're mowing, go slow. Hidden ruts, depressions and raised areas can roll your tractor (been there, done that). Even experienced professionals go slow go on unfamilar turf.
When you're done or taking a break, stay on the tractor until the cutter's blades stop (which takes more then a minute on my 5' Land Pride cutter).
Also, keep an eye on your tractor's temperature gage (if it has one). Brush cutting generates a lot of dust and can clog your radiator grills (I carry a 2" brush...trimmed the bristles to about 1/2 inch).
I'll also suggest using a dust mask, ear and eye protection.