ok........here we go. hope everyone just took a dump and has something to drink. cause this is going to be long.
as far as books go. i have read "secrets of solo racing" by henry watts and am currently reading "going faster" by the people at the skip barber racing school. i recommend them both.
slip angle-the difference between the direction the tire is pointed and the direction the tire is traveling. high slip angles translate into more cornering force, but, slow the car down at the same time. optimal slip angle is around 10 degrees depending on tire, and car. high hp cars can be faster using higher angles, as they are able to recover speed better. lower hp cars (yes that's us) lap faster with smaller angles (perhaps 7 degrees). of course this is nearly impossible to tell while driving. the best way to tell is alter your slip angle and check rpm at track out point each time through, the slip with the highest rpm is obviously the fastest.
constant radius turns.....
as has been stated before, you want to travel a path that yields the largest radius from turn in to track out. and as you know, this means getting right down to the apex (geometric). hipposleek is right about the steering action through the turn. from your turn in point, the wheel will smoothly move to a given angle, once the apex is reached, the wheel is smoothly unwound. one good way to practice is put a piece of tape at the top center of the steering wheel (same as that stripe you see on some aftermarket wheels), this makes it easier to tell if you are smooth through the turn, or if you are "sawing," at the wheel.
decreasing radius turns.....
"good guys don't turn in too early." -quote from an instructor i had. no place is this more true than on the decreasing radius turn. if you turn in too early, and with the radius you are currently on, your path will take you right off the track. anyway, you most definitely want to take a LATE apex through these.
increasing radius turns......
just the opposite, apex early, and do most of your turning towards the end, since the track is opening up for you.
the hairpin......
these suck. high hp cars can essentially turn a 180 degree hairpin into two 90 degree corners. us on the other hand, it is typically best to take a relatively late apex, like any other constant radius turn, and try and maximize our track out speed. there are as many approaches to hairpins as there are types of hairpins, you really just kinda have to figure it out for yourself.
real world cornering-
better than geometry
of course the entire track isn't made of 1 turn. our geometric gets us through the corner faster, but what about what comes after the turn? typically, a corner is followed by some sort of straight, it is because of this that the speed we ultimately care about (typically) is the track out speed. and if we late apex through a constant radius, we can gradually increase our working radius after the apex, effectively increasing speed down the entire straight.
surface changes....
many tracks have concrete patches on them in various places. these patches are our friends. they provide lots of grip in the dry (although they do wear on our tires). where ever these patches are is where we want to do the majority of our turning. lets say there is a patch before the apex. then you would want to go deep into the turn, past typical turn in point, utilizing that extra grip of the concrete, and take a late apex, allowing you to carry lots of speed out of the turn. (draw a late apex and you will see what i mean by "getting your turning done early). adjust accordingly for location of patches. this also applies to places on the track that do not have grip from oil/coolant/water/sand/etc.
changes in road camber.......
obviously if a corner is banked, you can go faster through it. sometimes a corner will be banked in the begining of the turn, but will be flat again, or even negative by the end of it. treat road camber changes the same as you would changes in surface.
multiple turns/esses/complex......
hipposleek can probably tell you about this one <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>
anyway, basically the only thing we care about is the final turn of the complex. whatever you have to do to get yourself to the turn in point that will maximize track out speed, do it. of course taking into consideration all the factors i just mentioned.
so yeah.....that's all i can think of for now. i didn't even get into threshold/trail braking, shift points, and other things because i'm only about 1/4 of the way through the book. let me know if you have any other questions. hipposleek, feel free to correct me where i have made a mistake.