Before we get into tracks where the outside line is the better line, let's get the inside line tracks out of the way:

Plates Tracks, duh. No one EVER attempts the outside
Road courses, simply because of the right turn element
Martinsville
Phoenix
Pocono
Indianapolis
Dover

And now, the iffy tracks:

Chicagoland
Darlington
Richmond
Atlanta

That means that alot of the intermediates, as well as Bristol and Auto Club, have an outside line at least slightly better than the inside. Note that the outside line also includes the middle line.

Outside Line tracks:

Kansas
Homestead
Texas*
Las Vegas*
Michigan*
Bristol*
Auto Club

*Middle line is better for these tracks

If you're going to use the outside line, what you'll do differs based on track. At Homestead, you just go into the corner the same way you would on the inside but get back on the throttle in the middle. At Kansas apply the brakes heavily until you get down to speed (Starting at 182 max and slowing to 170 min).

Homestead and Kansas were just described.

Texas: Same as inside line, angle in for going as fast as 185 miles per hour. Middle and outside lines are about even and both are better than the inside line.

Las Vegas: Same as Texas. The inside line could be the best line, if you could hold it at the 184 mph you're going.

Bristol: All about angling in. Same slowest speed as inside but more distance means more time to accelerate.

Auto Club: All about angling in. A solid entry into the corner can yield a maximum slowest speed of 184.

Well, no one ever uses it (Especially the AI and guys with setups), so lap traffic isn't an issue. The only real exception is online Homestead racing. It's the best line in plenty of tracks. Including plate tracks, but everyone goes to the bottom so quickly that the draft goes to the bottom, making Daytona and Talladega inside line tracks. Don't believe me? I've gotten my best single-car times starting on the outside and working to the middle on plate tracks. Especially Talladega.

Finding Homestead's outside line was easy. Just follow the other dudes. Texas was also easy: The car didn't ever GO to the bottom of the race track. Same with Atlanta. Darlington, I found with angles. Just barely faster so it's really a long-run alternative. Ah, Kansas and Auto Club. My two favorite outside lines. I was watching the Hollywood Casino 400, and Kevin Harvick dominated when everyone was on the inside. Dale Jr. and Jamie McMurray then took the outside line and both passed Harvick, and the rest of the field followed suit, leaving Harvick with no other laps led. I figured, "If NASCAR '14 is realistic at all, why NOT take the outside?" I tested it out, and, lo and behold, I was driving 10 miles an hour faster on the outside for a HUGE run on the straightaways. The high line in the Hollywood Casino 400 and NASCAR '14 Kansas. Note that McMurray pulled away from both Vickers and Keselowski following the image.

Don't be afraid to go for the outside line. Comment on if you find another outside line.