When buying a tent for your camping trips, always buy bigger than you think you need. That way, you are not going to be cramped for space when you go to sleep at night.
Of course, it is not the same if you are going to go backpack-camping and don’t know if you are going to have enough space to set up a big tent. In that case, buying smaller might be wiser.
Choose a tent that can protect you from air, rain, and snow, depending on the weather conditions of your camp region. Take extra protection if needed.
If you are not too sure whether you would like staying in a tent or not, try renting or borrowing a tent for your first time.