what can i safely delete to free up harddrive space?

i am a pc user moved to an imac...finding usual "claen ups" confusing because i dont know what types of files can be safely trashed to free up some space, like, can i ditch dreamweaver but keep therest of adobe programs or are they all entwined? can i trash dmgs after installs? i have mac tuneup and spring cleaning...seems i have lots of log files but can i trash them or would their removal cripple me? thanks in advance. lauri