When pitching your tent some common sense and a bit of planning will help to have a cool tent or build this simple DIY tent air conditioner.
Shade
The most basic and most effective step but I am always surprised to see so many campers pitching their tent in direct sunlight. A shade tree over campsite is gold, careful not to pitch it under obvious dead branches. If the wind picks up and you get a tree trunk through the middle of the tent your camp trip is game over. The sun rises from the east keep that in mind and workout where the shade will be in the morning. Its always better for some shade in the morning nobody likes to wake up in a sauna.
Wind
Note where the predominant wind comes from and pitch your tent accordingly to ensure that the breeze is directed through the openings. If you camp on a beach keep the sea breeze(daytime) and land breeze(nighttime) in mind they are great to move that hot air out of a tent.
Emergency blankets
Emergency blankets 
High Ground
If possible pitch the tent on the high ground air is forced up the hill and strengthens it. As a bonus you get a nice view and can not be flooded.
Water
Camping next to water always bring the temperature down, but keep in mind when the sun goes down the mosquito comes out of these areas.
Avoid
Avoid camping next to big rock features, the sun bakes them to blistering temperatures and they will radiate this heat out till late into
