Hey itzleena!
I see you have already been answered very nicely, so I'm just going to give my little responses too!
1. How do you find these official email to email celebs to ask for autographs? I came across two emails that ive written to different actors and recieved responses back so Id like to try the email route first. lol.
Yes,
Studio Fan Mail sends out
preprinted photos of their clients.

When I first started writing fan mail, I also e-mailed a few of their clients, but I now only keep authentics.

Some are very nice photos, at least! In an e-mail to an agent, you can just straight forward request an autograph/signed photo and remember to give them your address.
2. What happens if you write to a celeb at the wrong address?
If you've put your return address on the envelope, you'll get it back marked RTS (Return To Sender).
3. Do you just straight out ask for an autograph, or do you include an actual letter? I usually have trouble figuring out what to say to stars like say the Twilight cast.
No, I am first and foremost a fan so I write a proper fan letter from my heart.

You can write anything you want (there is no correct or wrong letter!) - tell them why you admire them, write a bit about yourself, and then, you can politely ask if they could send you an autograph photo.
4. Do you HAVE to send a photo to most celebs if you want an autograph back or can you jsut send a request?
No, most celebrities already have photos to send to fans.

I personally prefer the photos they supply and I rarely send my own photos (only when I have to) - I've had some great responses so far!

But you should always try to pay for the return postage, meaning you should try to either send an
IRC (when you're sending aboard) or a
SASE.
Hope this helps!

Feel free to ask if there is anything else we can help with!
Good luck!
zanne