Take the C line from Boston, and get off at one of the main stops in Brookline. Coolidge Corner is a great place to get off the train.
The D line, also accessible from many places downtown, will bring you to Brookline Village, a quaint area with many restaurants, though it isn't as big of a draw for people who live outside the area.
Cars and Brookline, like most of Boston and its immediate suburbs, do not mix perfectly. One thing to be aware of is that there is generally no overnight parking on streets; those cars on streets after 2:00 (11:00 in some areas) will be ticketed...seriously!
J.P. Licks - Sure, there are a few JP Licks in the Boston Area, but this one is still worth visiting. Incredible ice cream, cool neon decorations, and coffee when it is warm.
Rod-Dee Thai Cuisine - 1430 Beacon St (617) 738-4977: Amazing Thai food. Seriously. There is a lot of Thai food in Boston but this unassuming restaurant, busy most of the day, may be the best out there
Clearflour Bakery - has the most deliscious breads.
Ok, they don't have a website, but you have to go to Anna's Taqueria (numerous locations) for the best Mexican food in Boston. ~4
Also, check out famous Peno's pizza in Cleveland Circle. ~5
Vinny T's for good Italian food.
Courtyard by Marriot, Coolidge Corner
Safety is not something to be concerned about in Brookline. The town is incredibly safe, with an impressive police presence.