I prefer the tamarind pulp or extract as compared to the tamarind paste. I think that the tamarind paste is extremely sour, while the tamarind extract has a more nuanced taste - a mix of sweet, sour, and slightly salty. Here are instructions to prepare tamarind extract:
Buy semi-processed tamarind from either an East Indian or Asian (Vietnamese or Thai) store. The tamarind is usually sold as a slab - about 1 in. by 5 in. by 4 in., and wrapped in plastic shrinkwrap.
Cut out a 1.5in. by 1.5 in. piece. Soak in 1 cup of water and nuke in the microwave for about 30 secs. Make sure that the liquid does not boil over.
Remove and allow to stand for an hour. When cool, use your fingers to knead/massage the pulp. At this point, the liquid should be medium to dark brown. Continue the kneading until there are only few lumps left.
Strain over a medium fine sieve. Discard the solids retained on the sieve. Collect and use the extract.
Hope this helps. If you need links for online sources for tamarind, please leave a note in the forum and I will list a few sources.