What exactly do you think went wrong the first two times you tried to breastfeed?
No, there really isn't anything physically you can do while pregnant, except read up on breastfeeding!! I would recommend to read "The Womanly Art Of Breastfeeding" by the La Leache League.
How about finding out where your local ABA meetings are, and start going along. You will be able to get to know the local breastfeeders, and then when baby does arrive, you will feel that much more confidant asking for suggestions and support, if you need to.
When you give birth to the placenta, it is then that the hormones are released to tell your body to make milk.
Putting the baby onto your breast immediately after birth and allowing them to find the breast is very important, as is loads of skin to skin contact, and allowing baby unrestricted access to the breast day and night. It is the amount of nipple stimulation you get from your baby which tells your body how much milk you need, so don't use a dummy, all the sucking, breastfeeding and just comfort sucking, needs to be done at the breast.
For the same reason, do not use bottles.
I had both of my boys in a sling when they were tiny, so they were pretty much at the breast all the time, and could snack whenever they wanted, and I could get on with my day, hands free.
Taking good care of your own health is important, eating a nutritious diet, and drinking as much water as you need. Something which can help to cut the stress levels is to have frozen dinners made up in the freezer so you can have a decent meal in minutes for minimal effort.
Eating Oats helps supply, as well as linseed, and brewers yeast. I have the oats and linseed as a breakfast cereal.
If you do find you have low supply, then you can get mothers milk tea from a health food shop, or can take fenugreek.
There are tinctures out there which can help boost supply as well, but most 'low supply' issues are actually misdiagnosed, baby may simply be going through a growth spurt, and you begin to think you have no milk, or you are unable to express much, so you think your supply is no good (I cannot express, and I am currently tandem nursing) Also, at about the 2 or 3 month mark, your breasts do begin to feel less full, and this is beacuse your supply has settled down to exactly the right levels.
The website www.kellymom.com is a wonderful resource for anything to do with breastfeeding, the woman who runs it is a Lactation Consultant.
All the best smile
homebirthing mum to three boys!