To add a little more input on making LPs to what my buddy fortine_oo posted above... here is a 10 step reflap procedure for dummies. A beginners guide.
Preliminary procedure. Get good at the track. Get a good stable setup under you. Drive a couple of hundred laps before you make LPs. Know what you want and where you want it. Don't try to make them cold on a track, other than to just create basic LPs that the AI can follow that you know you'll modify later.
1) Go into testing mode and to the track.
2) While in the pits hit <ctrl><alt> <shift> <~> (last one being the far left key on top row on english systems). This will turn reflap on. Red text will show in the upper left corner of the screen.
Drive
4) When you're ready to record an LP (after properly warming your tires, getting used to the track, etc.), go to far chase view (so you can see the next step immediately)
5) Hit <alt R> and then <ctrl ~>. The Yellow triangles are the ones you're making and coming out behind your car. The orange triangles (at this time) are the track's centerline.
At this point...
a. For maxpanic and minpanic, you can probably stay in chase view.
b. For minrace and maxrace, I tend to run from roof view.
c. For race..... I run cockpit.
d. To get a copy of limp..... drive the bottom of the track or a line that is out of the way of the cars racing on the track and will take you by the pit entrance.
e. For pit0 and/or pit1 lp's, I tend to run from far chase so I can see what is coming well in advance.)
6) Drive the line you want to drive - fast, but smooth. If you screw up a portion, just drive another lap. The faster you go, the faster the LP will be. The smoother you go, the smoother the AI will be. If you lift and do throttle modulation to control the car, the AI will lift really big time when they follow it. Do not throttle modulate! Be smooth on the throttle. Let off, ride it and accelerate. Don't accelerate too soon. LISTEN to your engine. If you hear even a minor drop in rpm, do another lap. Trust me, you'll regret it if you don't.
7) When you have driven the perfect lap you want and gone thru the last portion that you screwed up... hit </> to save the line in a temp file. The yellow triangles will change to orange and the orange centerline triangles will disappear.
NOTE: Sometimes, if the track is really difficult and you can't take your eyes off the track or your hand off the wheel... call someone into the room to hit the </> key for you like a friend, your wife or son.
8) Unnecessary step: hit <alt R> to turn off the yellow triangles you are still creating. That will just clean up the view so you can better see what you have recorded.
9) Drive a full lap looking at the (now) orange triangles. Is it what you want? If not, repeat above. If it is what you want, hit <ctrl /> to save.
10) Exit the game. The line you saved will be named reflap0.lp in the track folder.
You can make as many LPs as you want in one session after saving...... just remember what you're doing.
Oh........ and PLEASE, don't forget to SAVE (<ctrl />) after you check out your orange LP before exiting. I wish I had a nickel for every time I've gotten in a hurry and exited without saving the dang line from the temp "stash".