Score a run every other game at home. Play some dudes who can't hit. Standard stuff, really. Unless they can make a trade.
The answer to the question posed in the headline is simple: Wait for Hunter Pence to get healthy, first, then wait for Norichika Aoki to get healthy. The Giants started the season with four capable outfielders, and by the end of June, if not the middle, they should all be back.
Why have easy answers, though, when you can make things more complicated? And in this episode of McCovey Chronicles' "Rosterbation Junction", we talk about what the Giants might have to gain by acquiring another outfielder at the trade deadline.