over and over.
that's about how to practice them.
Another approach:
Step by step perfect any and all sleights/mechanics individually.
Once satisfied, put it all together, no script, and practice until it's second nature.
Use a mirror(or camera) to check angles, then use a wall or something similar (so you won't be use to the mirror in front of you to check everything)
Then create a script to justify any and all actions.
Practice it all together, both alone and in front of your 'first' critics (friends, family, magicians...etc)
Then proceed to whoever your audience is, shows, tables, random people...whatever.
In between each step, ask yourself 'how can I improve this effect?' and change it a little bit here and there to make it yours.
Basically all there is too it. Practice alone and in front of people, then practice actually continues as you perform it more and more, though it will be second nature by then.