Where you put your body weight depends on the chasis and setup, particularly castor, so really you have to do that by feel.
One thing they will look for is signs of fatigue, mental and physical, you would be surprised how many drivers take their hands off the wheel to relax them, or stop leaning because their muscles are tiring. When i'm assessing a driver for endurance racing in a kart I look for this and their race craft more than absolute pace, i'd imagine anyone assessing you for a single seater drive will be looking for similar things too.
Dont be shy to use both pedals on the tight corners, unless they start black flagging for it. Obviously you need to keep a feel of brake temperature and it does depend on the track, but i'll often two pedal on a hairpin - sod the lack of a differential and heated brake disks, anything to gain a tenth
.
Dont worry about tyre squeel, do worry about slide.
Look after the kart, show good race craft, finish in the top couple of positions in all your heats (you wont be selected for single seaters unless you are a winner), dont crash even if its somebody elses fault and dont worry about absolute lap time (they wont have a benchmark anyway).
If your opposition are all rental drivers then go out as early as you can in the first practice session they give you - make sure your innate skill allows you to lap all those who go out with you on their first run - they'll get faster quicker than an experienced driver (they have more time to make up), so getting out early and putting a whole lap on the field in a short test session makes you look good.
If somebody is beating you, watch them, study every move they make, and for the love of whatever diety you pray too be nice to them. Take defeat well and show a willingness to learn from your betters - no single seater team is going to be interested in a driver who doesnt listen, even if you know everything about single seaters and racing you dont know everything about their team.
Remember, they wont have benchmarks of what is a good time or isnt, they wont be standing there with a stop watch. Study your times sure, show an interest in your own performance and look keen to improve it, but it's more important to win all your heats (you should be at least podiuming each heat against rentals) and utterly destroy them in the final than it is to be 0.3 seconds a lap faster.
EDIT: Also, know where your weekest corners are. If you are slower than somebody - know where you are slower. If you are quicker than everyone but not gaining on 1 particular section - know what section. Identifying your faults is the first step to solving them.
EDIT2: I said camber and meant castor, which proves either that I was tired, or imperfect... well it was written past 2am
*
) so I'm just trying to prove myself to this single seater team to try and get somewhere with them.
