Once you have found a consistent line and braking markers - all great advice.
In fact your first step in speed will come from - LINE, LINE & LINE - learn to unlock the speed the track can give you, then work on driving faster.
The next step up will come from watching replays of the fastest drivers.
They will steal tiny advantages everywhere on the track - use the kerbs to their maximum, trim as much as you can from a chicane without getting a 'cut' warning. Those little lumps all add up and will usually give you extra speed onto the straight - which again adds up to culmulative advantages.
Learn to trail brake - this seems to work well in every sim I have tried. Just riding the throttle over the brakes stabilises the back end, so you can brake and get it turned more consistently.
The final few tenths will come from driving technique - some of the guys out there are doing clever stuff with the cars to get them back on the throttle earlier.
I haven't mentioned tuning (setup) yet....for me, I found that it helped to have a base setup I could be consistent with (at the very least you want to have the right gearing for the track). For some people, they leave the setup well alone and go plenty fast enough.
Controller - as mentioned above you will be amazed how much more speed and consitency comes from a quality controller (like the G25 pictured above).
Have a read of this...
http://www.nogripracing.com/forum/showthread.php?t=6061
Some of it is GTL specific, but most applies everywhere.
Pero is truly fast, the more powerful the car you give him the bigger the gap in time. I could (sort of

) race with him in some cars, but when you get the evil beasts like the Cobra or Pantera, forget it. His advice holds good and is backed up by the fact he has genuine 'alien' pace.