When fitting a snaffle bridle, some key points you need to remember are:

• You should be able to fit two fingers under the noseband, to assure it's not too tight and uncomfortable on the horse. A caissons nose band isn't actually compulsory and you can use a snaffle bridle without one.
• The browband also shouldn't be too tight on the horses head, causing unnecessary pressure, you should be able to fit some fingers under this part of the bridle too.
• The horses bit should be fitted correctly too, the bit should leave one or two wrinkles above the bit, you don't want the bit too tight that it's pulling on the horses face, and you also don't want it too loose that it is falling in the horses mouth and banging on it's teeth as it will cause discomfort. 
• You should be able to fit four fingers inside the throat lash, which keeps the bridle from going over the horses head.
• The reins when riding, should not be twisted and the metal parts on the end of the reins, should be facing inwards, towards the bit.

Keeping the condition of the bridle kept well is important, as cleaning helps the leather stay soft and supple, stopping the bridle from cracking which is dangerous, as if the bridles cracked and you pull slightly too hard, it could cause that part of the bridle to snap.