The DoH guidance is pretty straight forward and is probably a good place to start reading. Also, follow what your paed says as I guess things will be slightly different for your DD if she can't yet sit up unaided - a baby chair on a slant will be ok of she's having runny purees.
If you like prescriptive stuff to follow, then Annabel Karmel books are a-plenty - the complete baby and toddler meal planner tells you what to give, how much to give and when to increase it. - this approach is not for everybody though and I'd recommend you have a look at it in the library before buying your own incase you don't like it. I like her books, but it's a lot to pay for somebody to tell you how to cook a carrot and puree it!!!
Also, you might get hung up on the fact that after 4 weeks of weaning, your baby isn't up to 3 meals a day with two or three courses at each, or whatever she recomends.
general rule of thumb is introduce one food at a time, give it for a couple of days to make sure there are no reactions, then give another. start with fruit and veg, and get your paed's advice on when to introduce protein - if you wait till 6 months, there's less chance of allergies anyway, so most people move quicker than carrot puree for 3 days or whatever, but I don't know about weaning premmies. I waited till mine grabbed some food off me then started with mixture of finger food and mush, but if you're being told to start before she is able to grab food and tell you she's ready, then start with purees/baby rice and see how she goes.
BLW followers will advise the Gill Rapley book, but if you're not going down this route, then I'd give it a miss and borrow this book instead for finger food ideas.
HTH