hi vicky
harry is very fussy and sometimes latches on fine and gets a full belly and other days he wont have a bar of it, so since about the first week i have been expressing and feeding harry through a bottle the expressed milk when he doesnt latch on.
i started off with a avent isis manual breast pump, but when you express every three hours, after a few weeks i noticed my fingers were seizing up,( becasue of the repetative action ) and switched to an electric one. and one thing i have learned is that the right pump is essential.( your gonna be using it alot and for a while) i got a spectra 3 electric pump from www.anawiz.com after finding the website on this site. i aim to express about every three hours, but a word of advice, unless you want your milk supply to lessen you need to keep up with it.
i would also express when you have just fed or during feeding your baby. this is because harry knew the noise of the expresser meant food and half the time as soon as i started i had to stop and feed harry as he automatically ascociated it with dinner time! before you start make sure your not in a rush, and gently massage your boobs to encourage your let down reflex. (also looking at your baby or smelling his scent on some clothes will help you 'let down' you also need to be relaxed, and try not to watch the pump.
i find expressing is only really effective first thing in a morning when you have rested. its also important to drink loads of water. i developed mastitus not long ago and the doc told me that its because harry wasnt latching properly my breast wasnt draining properly, so when you express i was advised to fully empty at least one breast (if you need the other to still breastfeed, rather than just empty half of both. the health visitor also told me that a babys suction is much more effective than an artificial pump so its a good idea to still put the baby to the breast even for just a short time as the milk production will be much better. i used to feed and express at the same time when poss but now harry is just too fidgety.
hope this helps
good luck hun. xx