I have signed a contract with my employer that if I leave my employer, then for 12 months I will not provide directly or indirectly any service to the client.
How good is this agreement? Can it stand in the court? My employer has not given me any proprietary software training to be used at the client site.

This is more of an employment law question. Generally, non-compete agreements, when understood and signed, as long as they are not unduly restrictive, are enforceable. Was the agreement signed under duress or were you not given full disclosure?