First question what type of gate are you wanting ? Driveway and garden gates are the most popular but there is a vast range of gates available from amazing gates for anything from a small entrance way and driveway gates to large scale industrial sliding gates. The main materials gates are made from are metal and wood.
Other questions to consider:
What is the purpose of your gate?
Where is it to be installed?
Do you require automation?
These are a few questions you need to ask yourself before you decide on a design.
You also need to make sure you have the correct dimensions and know the size of the gate you require.
Protecting your gate is also a very important step to ensure your gate can withstand not only the elements, but also continual use and stand the test of time.
The final appearance of your gate then needs to be considered ie Different paint colours available,