I really don't think you should take advice - if you've got LFS down so that you can "feel" slides etc before they happen, when you step in a real car / kart it'll all be natural.
From my experience in a rental kart series (one before LFS / STCC and one after) I can say it really helps.
Think about the kart, and just realise it's limits / strengths:
Rear Brakes - It's like stopping a car with the handbrake, basically - you can't stamp on the brakes and expect no lockups / straight braking.
Supreme Grip - Much more than you'd expect if it's a good day, and usually you'll have to really push to get it out of grip.
Low Power - Keeping Momentum is key - don't expect huge powerslides, rather it'll just bog down. Also, you don't really need throttle control tbh - I only ever modulated the throttle about twice per lap when I was at Red Lodge, and once was deliberately to de-stablise the kart for the entry into a corner and the other was just to bleed of a smidge of speed.
Indoor Tracks - Paint Matters! Painted areas are slippier than non-painted areas - at the indoor track I used to go to you could slip the back wheel on the painted strips where the barriers should be (but weren't) as they were on the outside, slam on the brakes and the kart would automagically steer into the corner for you, and made a great show for the guy behind you who thinks your crashing and "avoids" you...
The above ONLY applies to shitty rental karts, though.
Most of all - Have fun. It's only a friendly little race, it's not like paintballing or anything..