There are many factors which make various magick spells to work and have the potential to work.
Get to know about all of them, and also read about spell casting tips, optional steps and recommendations.
I will sum it up for a little, give you some recommended links about recommendations, optional steps to follow and tell you some stuff about important things.
Having the proper spell.
I agree with Catnip when she said that it depends on the spell you cast specifically.Firstly, to make sure that the spell has at least some potential to work, you have to make sure that the spell is a real magick spell that is actually connected to magick and its practices.
Just remember that there are two types of spells:
Real magic spells - These are real magic spells that actually work for the magic practitioner if he/she casts it properly. Such spells will work for you if you know what you are doing, if you are experienced and familiar with the basics, and work better if you will choose to follow some optional traditions like : colors, planetary days and hours, moon phases, ritual tools and supplies, etc. Such spells always worked for me if they were cast properly, since they are magic spells that have potential to work,. Do not forget that this is about potnetial, and such spells really have it. By saying real magic spells i mean that these are magic spells that can be cast by magic practitioners. Such spells do not include physical changes and DNA changes, or any actual kind of transformation. This is the other sort of spells i am going to talk about.
Fluffy / fantasy spells - Such spells are not real magic spells. The magic practitioner will not be able to get results from them even if he dedicates as much energy as he can, and even if he / she follows all of the traditions and optional things. It means that they have no potential to work. No matter what the magic practitioner tries to do, and how. Such spells include : transofrmation, DNA changes, and other kind of things which can be found only in science fiction movies. You are able to avoid such spells by : personal experience, logic sense and maturity.
This thing is very important. The proper spell has a lot to do with managing to cast the spell, it gives the spell most of its potential to work, as i said.
Now, after you know that you have to cast real magick spells (spells that have at least the potential to work), you have to know how to cast the spells properly and correctly.
To do this, you must know some basic magick concepts and practices which we call:
Of course that I told you about the fact that your spell has to be proper in order to have some potential to work. But, you do need to know what you're doing in order to use the spell's potential and make it work. Everything needs basic knowledge, although the action has a lot of potentail.
Here's a recommended link to the basics (guide for beginners):
If you have done this, and you already know what you are doing you can start to cast spells.
And now the last thing that might be helpful...
Tips, recommendations and optional steps
After you know about the important things and stuff you must follow, you can keep in mind that there are other tips and recommendadtions that might make your spell to be more effective and use its potential ! Everything has options that are meant to make everything more effective. But remember, this is optional.
So I recommend you to check out SoM's " Tips " tab, which talks about this sort of information. (moon phases, materials and supplies , mental condition , planetary hours and days , colors , etc) :
One other note: when you cast a spell you will not always be be able to tell whether it worked or not. Magic is typically considered to work along side the laws of physics. If you cast a spell, it will not do everything for you as it was a chocolate box. You need to gain courage and do what you need.