Put together a planning committee. Find other tennis players and share your idea with them. Post flyers at the local tennis courts with your contact information to generate interest. Take an advertisement out in the local paper with your contact information and the information for the first meeting.
Pick an organization or group to benefit and start working with them. While tournaments can give the money earned in the form of a prize to the best player, more successful events are those that involve charities. You could still do a small prize for the tournament winner, but pick a charity to honor, within the tennis theme if able. Start working with their community event coordinator, as they will have many resources to add to the success of your event.
Find a venue and set the details. Work with your planning committee through regular meetings and find a venue (your number one priority). This could be the local public tennis courts, if the weather is right, a local recreation center or fitness club or tennis school. Work on setting the rest of the details for the event as well. Determine if there will be raffle tickets and prizes sold, merchandise, other fundraisers, food or wine. Determine if there will be an after-tournament banquet to raise money. Consider all the options.
Generate interest for competitors. For the tournament to take place, you will need tennis players to compete. Start advertising everywhere with registration information to get them signed up. Charge a small entry fee and set up a play schedule for the day of the event.
Advertise and get the media involved; make this a top priority. Without anyone to attend the event, there will no monies raised or possible second tournament. Issue press releases, contact radio stations, news crews and other media outlets in your area. Go further than issuing the information before the event by inviting them to the event for additional coverage. Consider holding a preview event, too, allowing the media to play the court where the tournament will be held. Offer light refreshments. A preview event will allow the media to cover the event early and hopefully get even more attendees and entrants.