Here are some basic guidelines that will help you to run your competition.
1. Decide ahead of time what type of competition (if it is even going to be a competition) and stick to that. There are many different ways to hold a competition. For instance you can have just a display (no competition at all) display and competition, or just a competition. Or, you can have what is known as a Laurel prize tourney, where members of the order of the Laurel look at the items in the competition, and give out tokens to the items that they individually wish to encourage. Even if you run a straight competition, there are different ways to judge it - having a small set of judges, having the royalty/baronials/viceregals judge it, or having the populace pick the winner. There is blind judging, open judging and face to face judging. Whatever format you choose, publicize it ahead of time, and stick to it. Nothing upsets people more than to plan on entering an item based on one set of criteria, and have the criteria changed.
2. If you think that there will be a reasonable number of entries, consider dividing the competition into categories and putting similar items together. EG all textiles together, all food products together, all leather items, etc, and having a winner in each category either instead of, or in addition to an overall winner
3. Line up your judges ahead of time. Don't assume just because someone is coming to an event that they are willing (or have the time) to judge. Confirm your judges at least one week in advance, and make sure you have more judges than you need, as real life can happen to anyone, and one or more of your judges may not be able to judge on the day of the competition.
4. Coordinate with the autocrat about your space, tables, chairs, time, etc. requirements. Don't expect the autocrat to be able to read your mind, Let the autocrat know at least two weeks in advance what you need. And, be prepared to be flexible. While the A&S competition is of primary importance to you, it probably isn't to the event or to the autocrat, as other activities will be competing with you for space and time.
5. If your area has children consider having a special category for children broken down by age groups. EG, children under 12, and teens aged 13 to 16. However, if any of the children/teens wants to compete in the main class, against adults, let them. On the other hand, if you have an under 12 category, make sure that every child wins. Best costume, best use of color, best attempt in a new field, best whatever. Children 12 and under need encouragement not discouragement.
6. If possible, set up the competition in a central area that gets a lot of traffic. This way it is easier for people to see the entries in the competition. If it is visible, it is more likely people will go take a look.
7. Decide ahead of time what type of entries you are looking for. For example, items with a dragon theme, or baked goods, or items from Viking era Finland, or items made in the past year, or items made by a novice in the field, or anything from the SCA period. Whatever you choose, publicize it and stick to it.
8. Be sure to make it clear in advance what the criteria are for winning. This means explaining how the entries will be judged, and what the judges will be looking for. You do not have to use the kingdom criteria, but they are available to be used if you wish to do so. You can find them here. In any case, make it clear way in advance what the criteria are and stick to it.
9. Arrange prizes ahead of time. The prize doesn't have to be expensive; a scroll is a lovely prize. But there should be something for the winner. If there will be ten or more items entered, secondary prizes help encourage people. It is also a nice touch to have a small token for everyone who enters. It takes courage to enter a competition and you want to encourage participation, and get people to do continue to enter. Be sure to say something nice to each contestant about their entry, and to thank them for entering,
10. If you have a competition with judges, your judges are going to spend a large portion of their event day judging. Having small thank you tokens for the judges helps them realize how much you appreciate their time and effort. No matter what thank you tokens you give the judges, be sure to go up to each and everyone and say thank you. That is more rewarding than the most expensive present you could give.
11. Publicize the contest - in advance and on site. Make sure the competition is mentioned in the event announcement, on the web site, and on the mailing list(s). Arrange for heralds to announce the opening of the competition.
12. Be sure to arrange in advance for at least one person to assist you on site. You can't be everywhere at once, and having someone to help you makes things go more smoothly.
13. Bring plenty of supplies - judging forms, criteria, pens, etc. If possible, make up packets ahead of time for each entry. This will make the process go more smoothly for your entrants and your judges,
14. Announce the winner(s) in court, and be sure to thank everyone who enters, everyone who judged, and anyone else who helped you.
15. If you can do it, and this can be hard to arrange, try to have face to face judging. This is where the judge(s) sit down with the people who have entered and discuss with them why and how they scored them the way they did. If done properly this can save a lot of hurt feelings and misunderstandings.