The two main options are a UDRP complaint and direct legal action.
The Uniform Domain-Name Dispute-Resolution Policy (UDRP), administered by WIPO, allows registered trademark holders to challenge domain registrations that are identical or confusingly similar to their mark, where the domain was registered and is being used in bad faith. A successful UDRP complaint can result in the domain being transferred to you or cancelled. It is faster and less expensive than court proceedings.
If the domain holder is actively trading in a way that infringes your trademark in your jurisdiction, a court action for trademark infringement may also be available. For domains that are clearly parked for resale (cybersquatting), a UDRP complaint is usually the most efficient route.