I just can’t seem to do them in my dreams. No matter how much I tell myself to do them before I dream, I just can’t do it. The most common ones I’ve been trying are to look at my hands, the clock or other things. When I wake up, I feel like kicking myself for not doing it even though I had my mind set on it before going to sleep. This is very frustrating.
Do you do them constantly throughout the day? The main thing to focus on with RC’s is to do them regularly throughout the day and make it into habit. The idea is that you dream about what you do, so if you always do RC’s in waking life, you will eventually find yourself doing them in a dream and… voila! Lucidity! 
It is my opinion that you already have to be somewhat lucid in order to do a RC, at least lucid enough to actually ask the question of whether you are in a dream or awake. Thus, RCs are not so much a way to get lucid as they are a way to enhance lucidity.
Therefore for your RCs to be effective, you have to:
- Make a habit out of them, so you will do them ‘by accident’ in a dream just because the particular action is so common for you that you dream about it. (I don’t think that works very well, or anyway, it is too difficult to implement in practice.)
or
- Make a habit out of questioning reality (my personal favorite, though be aware that it’s not very useful in WL - on the other hand, no one will ever notice).
or
- Put your mind in a state of questioning reality for a particular time (for example, using WBTB/MILD or WILD).
Or any combination of the three.
took me a month to start doing RC in dreams just keep determined and you are bound to get it.
Personally, I think you’re better off convincing yourself that you will be lucid in the first place, and then do RCs. I mainly do RCs for safety’s (and sanity’s) sake, not lucidity-- although it might help to do them more often, might help get me out of more dreams that way, but dream signs are generally easier to see (and more entertaining)
Ionflux, i have to compleatly disagree with your comment here
When i first started out many years ago, RC were my way of gaining lucidity, i was not lucid to start with but the habit of preforming the reality test soon found its way into my dreams and when something different happened from normal, because i was habitualy checking for it and aware what would happen if the test failed, i realised i was dreaming.
Although it is true that RC can and are used as a way to enchance lucidity, they are also a way to gain lucidity.
Different ways are for different people. RC worked for me, i used to have maybe 1 lucid dream a month if i was lucky, then it came to a point where i was having 1-2 lucid dreams a night. It just takes a bit of work, and most of my early lucid dreams were started through RC.
PlasmaShock, try and set your self a trigger. By this i mean everytime you see something you do a RC. Go through your DJ and find a common something, ie clocks, soccer game, or a school. If it is a clock that you see in your dreams, in waking life, every time you see a clock do a RC, and i mean every time. Before you know it you will develop the trigger of doing a RC when you see a clock. Then when you see a clock inside a dream the trigger will fire and you will do your RC and there you have it lucidity.
After some time, develop the triggers to just the dream enviroment, so that every time you see a dream you do a RC. to do this you will need to imagine the eviroment and do aRC, this is all in the waking state. Then it will again seep over into the dream world.
Make sure that when you are doing RC you arnt just half ass doing them, you really need to ask the question and look for an answer, done just brush it off as being awake because you will end up doing that in your dream. Choose a few RC for different situations, and keep in mind what you are trying all of this for. its not just to see if you are awake now, but to see if you are dreaming later. Tell your self by using MILD that the next time you are dreaming you will do aRC to become lucid.
Keep it up good luck, let me know how you are going in a week.
Cheers
Well, someone had to, sooner or later. 
Okay, that would be the “habitual RC” approach, where you get into the habit of doing RCs without conscious involvement. This is what I doubt is effective, but now you said this as well:
This is what I would actually suggest: Ask the question “Am I dreaming?”. RCs which are purely mechanical are - in my opinion - of little help because the answer would be mechanical as well. You could easily fall into a dream logic trap and think something like “Ah, I have 6 fingers on this hand, so I must be awake!”.
You have to really consider whether you are awake or asleep in order to avoid such false conclusions.
But then, if you make a habit out of questioning your state of consciousness, why bother with the RC? They are fun things to do sometimes for sure, but the bottom line is, you have to ask the question and consider it as consciously as possible. This is also the only thing that can make you question a successful RC if you are dreaming.
Some of my LDs (especially the earlier ones) certainly started with RCs. Still, I now doubt whether the RC was the actual trigger of becoming lucid in those cases, or it just coincided with becoming lucid and was the first action (as I had set my mind to do RCs in my dreams, it may have been the first lucid action to do a RC).
Each lucid dreamer should of course do whatever works best for them. 
Hmmm, well posted. Makes you think about it thats for sure.
I have been thinking about my first lucid dreams and i have to admit that a reality check out of some of them was an act of lucidity, but, other lucids were a product of habitual but conscious checking of the enviroment…
well Ionflux, thanks for the food for thought, i should disagree with you more often 