PLEASE DO NOT BUY A COMMON PLECO! What the pet store will fail to mention is that the plecos they sell will get up to 24" in length... obviously NOT a good choice for a 10-gallon aquarium! Something we have found, which are a little harder to find but ARE sold occasionally by petsmart/petco is an albino bristlenose pleco (not the same thing as an albino pleco). These guys are great algae cleaners, have a nice bright pinkish-orange color, and will only get to about 5" when full grown. The otocinclus that Climbingspider pointed out are also a great choice, and are compatible with the bristlenose plecos.
With that said, the next thing you need to look at is the light for growing live plants. We have been using 6500k bulbs (sold as a 'daylight' bulb at walmart and Lowes for cheap). If your hood takes the screw-in type of bulbs, walmart sells a small 10W CFL bulb (looks like a corkscrew) in the 6500k spectrum that works great. This spectrum of bulb does wonders for plant growth in our aquariums. As Fishtanker said, you want to try to get close to 2W per gallon of tank (that's fluorescent watts, not that 'same as' wattage where they compare to the light from a regular bulb).
Plants -- I will agree with the crypts and the ludwigia. Both are nice plants for a smaller tank, and with good lighting you'll get some great greens and reds out of them. The java moss is a fast grower and can be used for great landscaping in the tank, but will easily take over if you don't keep it trimmed back (we just trimmed back a ball from our 80-gal that could easily fill a 10-gal... I threw it out in my pond, and the fish love it). There are a lot of varieties of dwarf grasses that will grow great - they propagate by sending out runners, but it can take some time for them to fill in. We also have some type of dwarf water lily that has these fantastic dark-red leaves... wish I knew the name of it.
My wife swears by the flourite... these days any new tank we set up has some in it. She puts down a thin layer of gravel, then the layer of flourite, then another layer of gravel on top. The plant roots get into the flourite and grow like crazy.
You might also want to consider filtration... The smaller your tank, the more important heavy filtration becomes. We generally buy filters for double the tank capacity listed on the boxes, and go from there. Depending on the type of fish you have, you may be ok with the basic air-driven foam filters, but if your fish have a high waste load, try to find a filter that has carbon packets and some kind of media to provide biological filtration.