Chamois cloth for leather, specialist cleaning for suede (not that I have any suede bags now) and a damp cloth for fabric, sometimes even a gentle go in the washing machine depending on the material. So far, so good!
I posted a cheap and unexpected tip a while ago. Foohy Pink Pet Erasers. They are not like normal pencil erasers. They dont smudge and they barely crumb up after use. They even feel different. N E hoo I use them on my leather bags (white Italian pebble grain leather bags at that) and it erases the marks right off! Sound silly but they work and I havent and wouldnt use any thing else. I bought them for my daughter and notice how well they worked on her homework and started trying them out on just about everything. Call me crazy but hey they really work.