01 Use the right flour
02 Butter is the key to success
03 Allow the dough to rest
04 Don't speed up the process
05 Use a ruler
06 Practice makes the master
A lot of French croissant recipes use pastry flour (T45) which makes for a croissant with a light, crispy texture. All purpose flour is also a good option. It will make a slightly more chewier croissant.
To make the block of butter it's essential to use "stable" margarine because it won't leak easily. Do NOT use spreadable margarine because it will leak and the whole recipe is going to be a big mess.
After every folding allow the dough to rest in the fridge until the dough is cold to the touch. This will prevent the butter from leaking when you flatten the dough for the next folding.
This rule goes hand in hand with the previous one. Be patient when you make croissants, don't try to speed the process because this will mean that the butter into the dough won't have enough time to cool down.
Any good croissant recipe will give you precise measurements to follow. Use a ruler or tape measure to measure the dough when you flatten it. This will help you get perfect looking croissants.
Making croissants takes some practice. Maybe the first time they won't be perfect. Try making the same recipe again and again and you'll see they will get better and better.