I have my first 'donation' in the freezer waiting for collection!
My experience so far:
You need to contact your donor centre and someone will come out to you or you'll be sent information & forms to fill in about yourself / yor lifestyle.
No more than 3 caf drinks a day or 2 units of alcohol a week. No smokers or drug takers accepted.
You will need a blood test - similar rules to giving blood about what would mean you aren't suitable to donate.
They will take milk from after 6w, ie after your own feeding is well established.
They provide sterile bottles, you provide everything else.
Strict hygiene rules apply, you fill in a chart about hand washing/sterilising etc. all milk is tested for bacteria and can't be used if contaminated in any way at all.
You need to record the temperature of your freezer daily, it needs to be around -19c, and you're given stickers to our on the bottles with your name/info on, and you record the date/time of expression. If you plan to express daily you'll need room for 14 bottles (about the size of small baby bottles, I think they're 120ml)
You can donate as much/little as you can, and they collect here every other week.
The only issue I am having at the moment is that 6w/o DD1 is an eating machine and I'm not getting chance to express because she's feeding so frequently. I'm sure that'll settle though!
Good luck with it!