Avoid large snails, small ones won't damage the utrics.
Leave the tank to settle before introducing the utrics. Grains of peat still floating after a few days can be removed with a seive. The water ought to be a dark yellow-brown, but very clear. If you put the utric in there while there is lots of peat floating around then particles of peat will stick to the plant, providing a perfect location for the attraction of algal particles and a rapid colonisation of the plant by algae. You want the plant as clean as possible to remove anywhere for algae to get a grip - as it were...
Use plants to leech nutrients from the water. I use Carex panicea, Typha minima and Eichorrnia crassipes - all are small and the latter can just be thinned as appropriate. The dead leaves of typha and carex are allowed to fall to the bottom of the tank, where they release humic acids which acidify the water a little and deter algae, as well as benefitting the utrics. If bullrushes or robust carex spp grow near you, collect some dead brown leaves, chop them up, boil them well and lay them on the top of the gravel base to deter algae (but this really is optional!).
Avoid flowering plants or regular pond ornamentals as accompaniments - there will not be enough nutrients in the water to support them and they won't generally flower. My water hyacinths are now very stunted!
Daphnia from a local petshop (sold as fish food) can be a quick-fix if algae starts to take hold. If algae really takes over the tank there is nothing to be done but start again with a whole new load of fresh water and with a cleaned utric. Again, leave the tank to settle before putting the plant back in. I use boiled rainwater.