Like any national park there are a number of rules to be aware of an obeyed. These can be found at each of the main entrances to the Serengeti (there are more than one) and are more common sense than anything else. The list of charges are also displayed and you can see why it is your local payment can get big rather quickly if you are visiting more than one national park. As can be seen from the sign, locals get charged approx only 25% of what tourists do which is just as it should be (though should it not be free?).
The Masai have been moved out of the Serengeti and the Ngorongoro Crater over the years but you will still come across lots of them living outside of these national parks.
You will find there will be lots of Masai women and children at any place tourists stop. They will all want to sell you beads etc that they have made and to be honest, they are not trying to rip you off. Life is not easy for them and money is scarce and therefore they will encourage you to take their photo, but for $1.
When you think that $1 is subsitance level in Tanzania you money does actually make a difference to them.
I think its important to respect other peoples space and customs,when taking photos or visiting villages its nice to offer a few dollars for the privalige although the tribes people of the serengetti dont need money essentailly,it can help with medical supplies etc and other handy items,i actually envy people living in the modern world who live of the land like they have been for thousands of years ,its environmentally friendly and if we all lived like this the world would be a better place :)
I think its polite where ever you are to ask first before taking photos and even more so with alot of the tribals of africa, i think it shows a lack of respect and appreciation just to snap people like there exhibits in a zoo,its even better to offer a few dollars for the privilage .One situation comes to mind when we came across some young massai tribesman going through there initiation to manhood and looked quite spectacular, but its a very personal stage of there lives so we asked first and then gave them a tip.