In Africa, yes, it is. Of course this is discretionary, and should depend on the service you receive. Usually this is done once during your stay at each place, just before you leave, and often there is a communal tip box for this purpose. Once you have booked your trip, you will be sent lots of information and details on your trip, including gratuity guidelines. To give you a rough idea the total cost of gratuities on an African safari may be about 5% of the total trip cost.
In Spain and France a tip is not common, although tipping loose change for meals and taxis is appreciated. However if you are with a guide for more than a day, your guide will appreciate a tip if you have been very pleased with the service you have received. Suggestions will be given to you in the information that you receive once you have booked your trip.
