A typical day varies depending on if it has a matinee or just an evening show and who you are looking after. If you are with the lead you only look after them, otherwise you might be solely responsible for a small group of other cast (usually 3/4) and also responsible for quick changes of other cast members of their dresser is busy with someone else at that time.
If I wasn't in rota for laundry and ironing and there was no dress rehearsal I would arrive a few hours before the show and head up to chat to the cast and check everyone was okay.
I would then go and collect any laundry and repairs and dry cleaning and make sure everything was where it should be.
I checked to see if there was a swing on as I would need to collect their costumes from a different area.
I would then go to either the dressing room of the lead star/s with the costumes and make sure they had everything they needed or if responsible for other cast members the area behind the stage where the other costumes are kept and the majority of the cast get changed and make sure costumes for the show are in the right order and pre set the first few outfits. This might also include putting trousers inside trousers and jackets inside etc to make quick changes easier. I would then go to quick change spots at the side of stage and lay out any costumes and sometimes props.
During the show I would be stage left or right to assist with quick changes. Some will help you and others will stand and let you do everything. This could be straight forward jacket changes or helping into animal costumes and on to stilts or corsets and such in a very small and usually pretty dark space. Or back in the main changing area if they have a few minutes to change before the next scene.
I stupidly thought costumes would be easy fasten or velcro or something before I started but nope!
If a costume rips during the show you have to run like hell with it to find the wardrobe mistress to fix it.
After the show you pre set dressing gowns for cast to get changed into and collect any underwear/socks and what ever is on the laundry list for that day and take the heavier costumes to dry and take any repairs to be done.
Best part of the job is when your cast group are fab, getting a few moments in between quick changes to watch the show from the wings (I love musical theatre so love this) and press nights.
Don't know if it's now changed but the worst thing for me was probably when you are in a receiving theatre which might receive a show for only a few months and some of them won't allow you any time off during that period at all as you take holidays in between shows (it's different if you are in the West End or touring with the company).
Not a huge issue as its only ever a few months over Christmas but it means no chance of going to parents evenings, sports days, school plays, nativity play and weddings etc!
That and you only have Sunday off and usually when you are off your friends are in work and vice versa.