You are required to purchase a tourist visa before you enter Uganda. Tourist visas can be bought in advance via the embassy or consulate in your country or simply purchased upon arrival at Entebbe International Airport or at any overland border. Photos are not required and a single entry tourist visa costs US$ 100 per person for up to 90 days stay in Uganda.
If you are planning to combine Uganda with a visit to Rwanda or Kenya it is recommendable to request for the East African Tourist Visa instead of a single-entry visa. This special visa costs US$100 per person and allows a 90-days multiple entry to Uganda, Rwanda, and Kenya. Regretfully, Tanzania is not (yet) a member of the East African community and therefore not part of this special visa arrangement.
How much to tip in Uganda depends entirely on your level of satisfaction of course, but even a small tip to show your gratitude will be highly appreciated. You might consider USD10 per day if you are happy with the service of your safari guide and 5-10% tip in upmarket hotels, Uganda lodges and restaurants.