I like the long sleeved Serengeti Safari Shirts from Cabela's. I don't take short sleeved shirts because I can roll up the long sleeves if it's too hot. The pants I use are also from Cabela's. I don't recall the model, but they have an elastic insert in the waist. My choice of color is either dark tan or dark khaki, or olive. I only wear pants and shirts made of 100% cotton. I find the synthetic blends too warm for my liking. A boonie hat is fine, as it will protect the ears and back of the neck from the scorching sun. I, prefer a baseball type hat, and i really lather on the SPF45 sun screen on my ears and neck. I wear several different types of boots, including a pair of Russells. Whatever your choice, they should be well broken in, comfortable, and quiet. I don't wear a "safari vest" - just don't see a need for it. If you like, PM me your email address, and I'll send you a comprehensive equipment list that's served me well over the years.

As far as what to expect - prepare to be treated royally, and have the best time of your life. IMHO one has to try very, very hard not to have a great time on safari.