Here are a few pointers to casting a sucessfull spell.
The Moon Phase: The Moon Phase Is a great deal when it comes to spell casting. The Moon adds more energy so you have more chance of your spell working, but it depends on your spell. Some spells work better on a diffrent Moon Phase. I would personally say the Full Moon works best for me but it depends on the Individual. Knowing the right time to cast your spell is very important aswell. I advise you set an intention on when to cast your spell. I cast mone at midnight on a Mull Moon. That's just me though.
Your Tools: When casting Spells I would have to say you would have to use the right tools. Many tools represent many purposes. The right Purposes will add more effect when you're Casting your Spell. For example, if I am Casting a Love Spell I would use a Red Candle because it represents Love. So the Tools actually matter. If you don't use Tools then you will have a less chance of your Spell working.
Your Intention: When you're going to Cast a Spell you need to be mentally focused on what you want to happen. You should probably meditate before even attempting to cast a spell. If you don't meditate your mind will be going on with random thoughts. A clear mind is a very important step. You need to put all of your emotion into the spell. You need to actually feel the spell working. Believing in the spell. When Casting your Spell Visualise your spell working. Keep doing that until you feel enough your have raised enough energy and directed it.
Experience: I actually believe it depends on the experience on the individual. We all know you should practice the basics for several months. After several months of practising you might want to try and cast a spell. Although I believe the more experience you have with magick the more chance you have got of your outcome coming true. Many people give up after there first attempt of casting spells. Dedicate yourself to the basics and follow the steps and you will be fine.
The energy: I believe the energy needs to be built up in the individual really well. Chants and visualisation will raise your energy. You will know when you're raising energy. For me when I raise energy my gut starts to get a strong energy feeling. The clearer you say it and the clearer you visualise it, your energy will get stronger and stronger then that's where you can actually cast the spell you have chosen.
Belief: You must believe the spell is going to work. When you believe you 'know' the spell is going to work. Instead of trying to believe, why don't you first try and get rid of your dis-beliefs. That will make it more easier for you.
Hope this helps the newbies and beginners. :)