Ensure all of the necessary equipment and facilities are in place. You will require some soccer balls, pitch markings (or cones) to mark a perimeter, corner flags, goal posts and a net (again, cones will suffice). Unless you have hired a referee, you will also need a whistle and a way to keep track of time.
Make sure that all the equipment you are using is safe and check that the pitch is clear of debris.
Determine the format of not only your tournament, but the number of players on teams. The number of players on each team will have a major impact on the dimensions of pitch you use, as well as the length of the matches in the tournament. For example, a 5-a-side tournament requires only half an 11-a-side pitch (which should be played across the width of the pitch) at most. A 5-a-side tournament could be as short as five minute halves, whereas in an 11-a-side tournament, you will want to play at least 15 minutes a half.
Do a draw to work out the group stages / first knockout stage. Study other, more famous tournaments in order to work out a format for your tournament. For example, the soccer World Cup sees 32 teams compete at first a group stage comprising four teams in each group. The top two teams from each group then progress to a knockout stage. 16 teams become eight, become four, and then two in the final.
Play the matches as determined by your tournament format. If you have an odd number of teams, thin these out by either giving one team a bye, so the numbers are even in the next round, or hold a group stage where one group contains an odd number of teams in. If you have group stages, play them out first. If you do not, move straight in to the knockout phase.
Be sure to record all of the results and keep track of the goalscorers if you wish to give out an award for the top goalscorer of the tournament. If you have the technology at your disposal, you can administer the tournament using a spreadsheet program.
Complete the tournament and hand out awards as necessary. If you have trophies for the top goalscorer and the tournament winners, then hand these out in a presentation ceremony.
If you have hosted the tournament in a makeshift setting, be sure to collect up all rubbish and any items left behind—you should leave the premises in the state that you found it.