Hi Katherine, there's already lots of good tips here, especially the ones about various shawls, slings, etc. Just to say I was very keen to BF but my baby always took a while to latch on so it wasn't easy to be discreet in public, which didn't make me feel comfortable. In the end we settled for expressed milk in a bottle which seemed to work very well, and also was useful when my husband did some feeds to give me a chance to get some sleep.The general feeling about BF at home and bottles when out is that using expressed milk is generally better as baby is getting the same milk essentially, plus all the health benefits of breastmilk for the baby.
The advice with regard to mixing bottle feeding (whether formula or expressed milk) is to wait for about 3-4 weeks till breastfeeding is well established - ie latching on and taking a full feed easily, not starting and stopping - you'll soon know when your baby is getting the hang of it. There is a feeling that some babies might get "nipple confusion" - eg start refusing BF and only wanting it from a bottle, but I think the actual fact is that generally this is an idiosyncratic thing - babies will do what they want to do. Two friends actually waited so long that at 5 and 6 months respectively, the babies refused a bottle totally - one friend persisted, trying every single brand on the market until she found one that baby complied with, while the other gave up and never tried a bottle again. So maybe the timescale of more than 3 weeks, less than 3 months is a good thing to aim for.
Then again, some babies get both earlier -eg they may not be gaining weight or may be getting dehydrated and the mums are advised to add formula to BF - and are perfectly ok with no "confusion" whatsoever. The good thing about BF is that in some ways it is easier - no need to fuss around waiting for the boiled water to cool down to mix a feed (the advice now is not to mix a feed in advance for risk of bacterial proliferation) or stressing about measuring out the right amount of formula when you are tired and sleep deprived. Of course, in some ways it is less convenient as you have to watch what you consume - no knocking back the alcohol, or overdoing the caffeine, and you have to watch what medication you are taking. But it is certainly worth doing.
It can be a bit sore at first, so make sure you do have sensible and supportive friends to turn to for advice and encouragement, whether that's a breastfeeding cafe, post natal group or just friends who have already gone through it. The worst can be well meaning advice that actually undermines your confidence. And you don't have to sit in pain all day or stick cabbages into your clothes as some books or anecdotes say - comfortable plain cotton nursing bras (try them and get fitted if needs be before you deliver and make sure you buy sufficient numbers - once baby is born, the fewer chores and trips to make the better) are more than fine. And if it doesn't work one time, don't get frustrated - expressing a little milk with a hand held pump or electric pump will help relieve some pain from engorgement, while mentally it is reassuring to know that there's expressed milk in store if you have to use a bottle. Then try again. (Engorgement leading to overfull breasts is not easier for baby to latch on, it can be worse because the shape doesn't fit and baby just gets squirted but doesn't get a drink! So try out and buy a pump early - again, regardless of what tell you. Best to have it on standby.)
There's also a lot of mind over matter in BF I think - if you feel relaxed, it actually helps baby to feed more easily I think because you are both calm, and you can help guide baby to a comfortable position feeding better. So if people are putting pressure on you to get it right or do it quickly, tell them to get lost. Tell anyone who is stressing you out to get lost....or do something useful like taking out the rubbish! ;-)
All the best for your baby's birth!