You can use sp_helpindex tablename to find the indexes on a particular table. This will also give you the columns and the order of them in the index. As for rebuilding them, you have three options. Drop and rebuild, dbcc dbreindex, and dbcc indexdefrag. All three have their pluses, minus, and idiosyncracies. Generally I use them in the following way:
dbcc dbreindex: Small tables. This will create a copy of all of the indexes (remember clustered indexes are really the table itself), and do a quick switch to the new copies.
dbcc indexdefrag: Large indexes where the index is alone in a filegroup. Also, if the database is in simple recovery mode. I am not terribly impressed with the efficiency of indexdefrag, but it does not lock up the table. This is highly valuable for systems that can not be brought down for maintenance. On the downside, it will run your transaction log pretty well, if you are not in simple recovery mode.
drop/rebuild. A decent all purpose tool, but you need to have a bit of downtime available to you, as the tables will have select locks on them, while you rebuild the indices. You also need to have the scripts for the indices handy (which is why I encourage the use of sp_helpindex), in case anything goes wrong. Remember also, the clustered index should be the last to be dropped, and the first to be rebuilt. Also, note. This does not work on Primary Key indices that have a foreign key referencing them.