I just usually look the other way and keep driving, although it's hard to avoid them when you're walking around and looking. Hopefully the line up is far enough away I can see them coming, jump back into the car and leave.
Last month I actually had a sales guy follow me around the lot on a bicycle!!! "OK pal, you just keep on following me and we're gonna ride each and every row of cars you've got!" I think I even repeated a few rows for good measure before I sped off to the competitor's lot....
Different town and dealer, I had a pushy sales guy who felt compelled to READ THE ENTIRE window sticker to me, line by line!!!! "Dude, you're not reading that to me are you? Cause' if you keep reading I'm leaving, I know more about this car than you do...." Learn your products on your own time not mine..
The huge mega dealer in town (something like 17 brands) is my favorite though, the lot is always open to cruise and rarely does anyone come out and bother you. They don't haggle on price (at least that's what they say) so there isn't the pressure like the other dealers. "You wanna drive this Mr. Customer? Sure thing, here's the keys, have fun and come see me when you get back". Thats the way it should be done..
Now if I could find the dealer who has all the doors unlocked! That guy would have plenty of my spare browse time.....