The northern parks lend themselves to 7-8 day safaris whereas the southern parks can be visited for a shorter safari. When to go Broadly speaking the times to avoid are the rainy seasons. The heavy rains fall in April, and May, and the light rains fall in November. From the rest of the world We would recommend getting a cheap flight into London and flying on. Alternatively, one can find a direct flight from your home country.
Emirates seem to offer good prices from South East Asia.
Types of safari Broadly speaking there are 3 types of safari. A mobile permanent safari - in which you visit a number of different camps and lodges as part of your safari. Most appropriate to Northern Tanzania Classic mobile tented safari - Instead of staying at different lodges, you will stay in a temporary camp set up for you each night.