Tips on checking compression

Warm up the engine first to get the oil flowing and everything up to temperature. This will make taking out the plugs less fun, but the rings will seal better and your bearings will thank you.

Pull all the spark plugs. The engine will spin faster, and the oil will stay on the rings longer (no compression in untested cylinders to push the oil past the rings)

Don't "put something in" the carburetor. You want to hold the throttle wide open, so the engine can pull all the air it needs. Brick on the pedal, wire the linkage open, whatever works best. You do not want to be letting the pedal up and pressing it back down after each cylinder, this will fill the engine full of fuel and wash all the oil out of the cylinders.

Crank each cylinder the same # of times. Usually max compression is reached by 3-4 compression strokes.

Be consistent. Always do your compression checks the same. That way, when you do one later, they're comparable. The speed that the engine spins makes a difference, so make sure your battery has a good charge. Getting a baseline for your engine is good, although it won't necessarily tell you "how long it will last". It is handy for diagnosing new problems though, and can give you a basic idea about how well things are sealing. A leak down test is more accurate for telling engine condition IMO, but a compression check is a good place to start.