Its quite not a legid question.Belief and intent are not substituable.Belief is having faith in something that it will work,whereas intent is your wish or want which you express for the spell to work,its hard to explain.
Belief and intent are each important in its own way.Having belief but not putting your intent is like having faith that you will pass in a exam,but do not study.It will only bring failure!Have 'belief' in the spell that it will work and while casting it,put your 'intent' in it.Thats it!If you are doing a wish spell,put your intent,for what you want that wish to come true.If you are doing a curse,put your negative intent in it!
Now if you understood what i said,then its good,if not maybe others ane explain better :)
go here to read the basics:
after u learn the basic u can cast a spell. How?
Ok,The real secret of successful
spellcasting, as with all magic, is your connection to divinity, within and without. Your thoughts, willpower, feelings, and physical
exertions are actually all expressions or forms of this divine energy -- just as air, water, fire, and earth are all forms of divine energy. When you understand the true nature of the energy you work with, you can make real magic.