Kenya, Tanzania, Malawi trip - need advice!!!

Kenya, Tanzania, Malawi trip - need advice!!!

So this will be my first time to Africa, the plan is Kenya, Tanzania, and Malawi for certain reasons.  I have a buddy in northern Malawi and we want to climb Mt. Kilimanjaro.  What is the best way to travel around? Bus? I will most likely fly into Nairobi, but am open to suggestions.  If I could bus to karonga (northern malawi) then back to dar es salaam that would rock, is this possible??  i also want to do a short safari in there probably in Tanzania, maybe like 4 days.   ANY tips, hints, advice, warnings, suggestions, etc. are totally welcome and appreciated.  Oh and I am going in mid July for about 4 weeks.  Muchos Gracias!!!