hot chicks and little babies usually work wonders.
You can get minor league players and non-starters down on the lower fields daily. They usually sign when coming back up to the clubhouse.
Along the rightfield line is a good place too like mancini said. My little boy and I got Torii's, Aybar's, and Weaver's there.
If you go to another stadium when the Angels are visitors the team signs (usually along the left field line). Mancini, Cory, Kristen and I got Brandon Wood's and Mike Trout's autograph a few years back.
The best chance to get autographs tho is after the Tim Mead "state of the union" on Sunday. AW has early access to the stadium. We got Pujols' last year.
Good luck dude