From our experience, get yourself some good scales to be able to weigh them daily to make sure they are putting on weight. No weight gain - or even worse a weight loss is an indication that all is not well. I'm sure others can suggest what scales they use and I think digital kitchen scales are popular. I bought some luggage scales from maplin. Used to put the kittens in a old handbag and weigh them that way! Whatever you choose they need to be accurate in the region of grams.
For further info. including a good poo guide put the following into your favorites
http://www.kittenrescue.org/pages.php?pageid=15If you have a local cat rescue, speak to them as they may have someone you can ask advise from.
Also beware of constipation! If a kitten does not evacuate and crys after feeding then you might need to see a vet as the kitten is distressed and may be in pain.
When i was feeding I had a timetable of feeds I stuck to, on it I recorded the amount fed at each meal and who'd peed and pood. and also a space for a weigh in. Sounds daft but after a couple of weeks of feeding day and night (I had 4 kittens) you may find the lack of sleep can get you confused over the simplest of things. With hat in mind , if you can rope in one or two friends as soon as possible so that you can all have the same technique, its nice to be able to share the burden.
Finally, if the worst happens and they don't survive, try and not blame yourself too much. If you have done your best you have done all you can. Also don't relax until they are old enough to be homed - it's not just the first 4 weeks that are important and risky!
Good luck! Let us know how you get on.