I'll be honest, I am partially writing this because I always forget how to reset the identity column on a table and I want to be able to just pull up my blog and look it up. Yet again today I had to do this and I couldn't remember the exact syntax, so here it is. The next record is going to be the seed value plus 1, or in the case of this example I will use zero so the first record is 1. That will make my O.C.D. happy to see my table starting with a key value of 1!
DBCC CHECKIDENT('<TableName>', RESEED, <StartingValue - 1>)
DBCC CHECKIDENT('DimGeography', RESEED, 0)