Before you race
Now I have everything .... Can I race now?
Almost! .... you probably want to get in some practise first though. Before going out on a new circuit you should walk the circuit at least once when it is quiet (this goes for experienced drivers as well). Take someone who knows the track with you if possible. Look for places where the track is "forgiving" when you go off. More importantly, look for places that will break your kart if you make a mistake (high kerbs & drop offs eat sprockets, chains & brake discs!). Look for bumps & rough spots that may affect the handling or your braking distance. Mostly just get a feel for the lines and the track in general.
When you start off, don't try to be fast .... it won't work and you'll most likely break something trying (If you're lucky it'll just be your kart!) - Rather try to be smooth. Visualise the track before you start and try to stick to the lines you "saw". (You'll modify these as you get a feel for the kart). If possible, follow someone who knows the track. This can be invaluable as 10 laps behind an experienced driver can be worth 100 on your own. Remember that you only have limited time (and money) to practise. Do whatever you can to make the most of your time.
You also need to remember safety and etiquette. There will be faster guys on the track - They will come past you like you're standing still. Don't weave, stick to your line, drive smoothly, and they'll be able to go around you. If you panic and do something totally unexpected it can result in an unnecessary (and possibly nasty) accident, which is not likely to endear you to your fellow racers (everyone can cite at least one "moron" who "almost got them killed"). If you know they are coming up on you, let them know on which side to pass you by pointing with your hand . They'll appreciate this, and your courtesy will hopefully be remembered when you need some advice on setup etc.
Once you are driving smoothly (consistently, not necessarily fast) it's time to fiddle with your setup. Every chassis is different. Every track is different. Every day is different. Don't be surprised when one person tells you to widen the rear track to increase grip and 30 seconds later another tells you the opposite ... it's all part of racing! If possible, have someone with more experience than yourself look at your kart on practise day. They should be able to get you in the ballpark with respect to sprocket size, track (tyre separation) and chassis torsion. The rest is then up to you.
Take your times for a few laps. Come in and change only one setting. Make the change quite large so the effect is easy to notice (eg. change your sprocket size by 2 teeth, move your rear tyres in/out by 20mm each, or tighten every adjustable bolt on your chassis). Go out again and take your times. Come in and compare times and make notes about how the kart feels (does it understeer/oversteer going into/out of a corner, does it bog down or over-rev, does it "hop" around corners, etc). You may be going slower now, but knowing how the kart reacts to various changes is important for future adjustments when conditions are different. Try to figure out what settings work best for a particular track under given conditions (hot, cool, plenty grip, not enough grip). Remember: All the time concentrate on driving smoothly. You can't be fast if you're not smooth.
Once you are within 2-3 seconds of the midfield runners, you are probably ready to race.
A few lessons at a karting school is highly recommended!