wrong things to do at a theatre?

Question:Going to a theatre in the west end of London tonight. Never done that before. Obviously I know the basics - turn off mobile phone etc. But what are the other little 'do's and dont's'? Is it OK to dress smart casual, or do you have to make a better effort than that? Do you get a break half-way through like at a football match to go and have a smoke/drink? Can you take a drink/chocolate into the auditorium, as you can at some (at least independent) cinemas?
Thanks in advance for any help on these and any other matters I should know.

Best Answer - Chosen by Asker: Going to a theatre in the west end of London tonight. Never done that before. Obviously I know the basics - turn off mobile phone etc. But what are the other little 'do's and dont's'? Is it OK to dress smart casual, or do you have to make a better effort than that? Do you get a break half-way through like at a football match to go and have a smoke/drink? Can you take a drink/chocolate into the auditorium, as you can at some (at least independent) cinemas?
Thanks in advance for any help on these and any other matters I should know.

Switch off mobile phones.
No photographs of any kind at any time in the auditorium.
No hand held games during the show.
No personal stereo/ipods on during show.
No talking or whispering (off putting to those around you.
Try not to bring sweets with noisy wrappers (nothing more irritating than crinkling of plastic/foil wrappers)
Try not to shuffle about in your seat (especially if you are tall and sat in front of a small person!)

Dress: Almost anything as long as it is not too revealing! You are sat in the dark. Gone are the days when you had to wear a dinner jacket!
In some theatres, you will be able to take drinks into the auditorium if they are in plastic glasses/bottles. Check when you get there as those theatres which allow it will usually supply plastic glasses. Please don't throw your litter on the floor. Find a bin (even if you have to wait until you get out onto the street).

You can usually pre-order alcoholic and non-alcoholic drinks for the interval. Most intervals are 15 - 20 minutes long. This should be stated either as an announcement or in the programme. Try to go to the loo before the show (men have less of a problem) as you don't want to spend the whole interval queuing!

Do not get out of your seat at the beginning of the show and rush to any empty ones closer to the stage. Just because they are empty, does not mean that they are available. Most shows have late-comers points which can be at any point during the first half of the show. Some people stand at the back until the interval and then take their seats. Nothing more embarrasing than being kicked out of someone else's seat!

Just have a good time! Hope you are seeing something good.

EDIT!
Just re-read your question and found the word 'tonight'. Hope you had a fun time!

Yes to all. Don't overdress, it's not needed.
You can go outside the theatre during the intermission for a ciggie and grab a drink from the bar.
Enjoy the show, whatever you are seeing. It's a great night out

Dress how you like - casual/smart is up to you. Most shows have a break somewhere in the middle that lasts about 15 minutes. No drinks in the auditorium are allowed. The key rule to any theatre is simply to keep quiet during a performance. Aside from that, don't eat sweets and so on because of the noise, and don't take photos.

Never ever shout "HE'S BEHIND YOU..!"

At some theatres, you can pre-order / pre-pay for drinks (at the bar, for drinking in the foyer), so that, at the interval, you've only got to collect them and not waste valuable drinking time queuing and paying.

if you sit by me in the theatre don't rustle sweet bags/wrappers and don't talk all the way through it or i'll give you an evil stare! or tell you to shut up! these to me are the worst things people can do in the theatre oh and one more thing don't be late!! i hate that too.
dress in whatever you are comfy in, you can't take pictures or anything.
yes there is an interval head to the loos first as it get busy. yes you can take choc and drinks into the auditorium but drink in plastic glasses.
above all have a nice time and enjoy the show