After a little mishap with my low pressure regulator, I found out a few stupid things that I did to my gun that I shouldn't have. So, here's a little basic maintenance page with some do's and dont's that I picked up from rec.sport.paintball and P&P techs.
First things first, here's what you'll need. A 50/50 mix of isopropyl rubbing alcohol (your mom has it, I guarantee) and water, some rags or paper towel, a clean workspace, a chamois squeege (the fuzzy one), synthetic paintball oil/shocker lube/etc. (not wd-40 and NOOOOO Vaseline), q-tips, Allen wrenches, and the smallest pair of pliers you can get.
Ok, here we go. Degass your gun, take off the hopper, all paintballs, barrel, and the bolt (because you'll clean here anyhow). Get the tip of the chamois squeegee wet with the 50/50 mix, and tip the marker upside down. Run the squeegee through the top tube where the bolt should be, slowly and twisting it. This should clean out any paint that may have broke as well as any old oil/grease from your bolt. Now run the dry end of the squeegee through, or wadded up paper towel if you don't have a double-sided squeegee. Make sure you get the feed tube as well, paint likes to hide there.
If you didn't get any paint near your trigger/trigger frame, skip this. Remove your bottomline, reg, and grip frame, dismantle, wipe clean all moving parts (sear, trigger plate, sear pin) and then relube with paintball oil. Reassemble the frame, wiping down with your rags and the 50/50 cleaning solution. Be careful not to get that stuff on the re-lubed trigger parts, otherwise relube them. Now that the grip frame is done, go ahead and clean your bottom line, regulator, and body with the 50/50 mix and rags/paper towels. I suggest applying solution with one rag and wiping off with another.
Take the q-tips and get the ends wet with the 50/50 mix. Clean out the area between all of the front pneumatics and the pneumatics themselves to get rid of the paint. You'll especially need to do this if you play without a shroud like 90% of cocker owners. Dry with q-tips. This should be your gun cleaned for the most part.
Now for the lubrication part. If you have a stock or non-delrin based bolt (IE it's metal) go ahead and put a few drops of oil on it. Lube any part that will touch the body, such as the o-rings and the fatter parts of the bolt. If you have a delrin bolt (IE Shocktech supafly or the orracle bolt) you don't need to lube, Delrin is "self-lubricating" and will swell if you lube it. Reinsert the bolt and pull pin. Now comes the part where I think newer owners will go wrong. You will want to run a few drops of synthetic paintball oil through your gun. However, you will NOT want to run this oil through the primary regulator (you know, the foregrip thingy). Heavy buildup of oil will get on the reg seat and dirty it, causing velocity fluctuations. So, unscrew the regulator, tip the gun upside down, put a few drops of oil into the ASA on the bottom of the cocker body, and screw in the reg. Keep the gun tipped upside down and screw in your tank (remember to cock first and keep your barrel off). Fire off about 20-30 blanks to make sure the oil gets into and through all the internals. Note that once the air is attached you can turn the gun right-side up. You will not want your barrel on when you fire the gun so that oil that's shot through the system doesn't get in your barrel and cause your shots to go astray.
Degass, and now you're done for the day. Do this every day when you get home from playing and your marker will stay in top shape.
Other interesting notes. The primary regulator should generally not need to be readjusted. Unless you change valves or springs, don't touch the pressure adjuster for the reg. WGP sets it where it's at for a reason. Should you need to readjust it, WGP sets the pressure at 350 psi stock from the factory for stock Autocockers.
Some notes on oil/lube. There are certain types of oil and grease that work well on paintball guns, and some that don't. Rule number one when considering a lube is - NO CARBON BASED LUBE. This includes oils such as WD-40 and motor oil. The carbon contained in these products will attack seals inside your gun, causing them to fail more quickly. So, don't use them. Now, almost any other synthetic paintgun oil works very well. PMI oil, 3-in-1 oil, Gold Cup, and the like are all acceptable oils. You can also use Shocker Lube (it's actually grease) on some parts of your marker, such as the 3-way shaft, seals (especially in eBlades), and surfaces, such as the hammer. It works well and doesn't gunk up too bad, unless it comes into contact with Co2. Generally though, I'd say for cockers, stick with your basic synthetic paintball gun oil.
I would recommend running some oil through your primary regulator every once in a while to make sure the seals don't dry up, however it's not something you should do after every day of play.