The most obvious way to keep your sponsors is to honour the agreed offerings to them in a professional manner but there is more. Here are a few things to think about in terms of the sponsorship relationship:

• Maintain the club's good reputation - no sponsor wants to be associated with a poor image
• Make sure that interactions with ALL of the sponsor's staff are positive. Let your members know who your sponsors are and reflect to them how important the relationship is and to support them where possible 
• Have a wrap up session with sponsor(s) to report on the year, to thank them and gather ideas for future years (function, meeting, presentation, report, email)
• Ask sponsors individually how it went, what they considered went well, any problems, and any changes they would like to see for next year - respond to feedback or send them a sponsor satisfaction survey
• The sponsor probably won't be keeping media clippings or copies of your newsletters etc. At the end of the season it is always good if you can provide your sponsors (particularly major) with a package showing them the club's achievements, and what they got for their dollar. The people you deal with often have to report also and this makes their job easier
• Try and get an early commitment for the following year
• If you have had a very positive relationship with a sponsor, ask if they would write a letter of support for the club in  terms of attracting additional support
• If a sponsor withdraws its support, it is always worthwhile knowing why.