I plan on becoming a writer/director and I'm wondering if it is okay to have camera directions in my scripts.
It is certainly fine to have directions in a script which provide information which is vital to the telling of the story (entrances and exits and key actions not made clear by dialogue are obvious examples) but you probably don't want to go into too much detail at the scrip stage. Obviously if you are directing it yourself you can do what you like but even so you should be wary of making detailed decisions at too early a stage and you probably want at least one version of the script which is fairly clean or it will become unreadable.
There may also be certain shots or effects which are really crucial in setting a scene (the opening scene of Star Wars being one possible example) but again for a general script these should probably be descriptive rather than technical.
Bear in in mind also that if you are pitching a scrip to other people they probably aren't that interested in camera directions at this stage, they just want to see if the scrip and story are any good. Adding too many notes will just detract from this.
Film is also an inherently collaborative process and if you are too prescriptive you are taking away the ability of performers and the production team to make creative decisions and it is highly likely that your initial ideas will change once you get to actual production.
Even if you want to both write and direct a project it does still make sense to keep some separation between the roles. By all means keep notes on your ideas for shots but these are probably best kept separate from the scrip itself.
Obviously one you get to detailed production planning and filming itself there will probably be dozens of different technical scripts floating around each with its own set of directions for sound, score, lighting, camera positions, effects etc etc
Equally if it helps you to keep directorial notes at an early stage by all means do so but it will probably be better all round of these are a separate, parallel document.
As an aside I recently worked on a stage production (on a very tight schedule and budget) where all of the lighting cues (which in this case were a reasonable analogy for camera shots on film) were worked out in an evening on paper with the production designer (me), the director and the stage manager, the second act didn't even get a technical rehearsal and it was all fine. Having said that this was at a fairly advanced stage in the production process when we all knew the show, the set and the performances really, really well.
You are the scriptwriter, not the director. Stick to the script, the locations, the characters and the dialogue. Your job is to write the script.
You can specify camera shots, angles, and such, but expect most directors will ignore it. Many places will drop your script if they feel it is too stuffy or with too much directions. Unless your scene absolutely requires a specific way to do it, stay away from giving too many details.
I agree with Chris, it depends entirely on who is going to be reading it. If you are going to be at the helm from start to finish then I would suggest keeping a separate copy of the script where you can write in cinematography notes. If you have a copy of Final Draft then that's all the better.
However, if you're pitching to an agent, I can't speak for them myself but I was always taught to cull any and all stage direction from your scripts, and the same with prose. You want to be clear with what is happening in scene and dialogue, and if you're spending time trying to tell some agent or cinematographer you haven't met how you want it to look on screen, your story may suffer for that. Entirely up to you obviously, but I would suggest either keeping them separate or do away with stage direction.