Use a quick release skewer to hold the freewheel removal tool in place.
Remember to loosen the quick release skewer after the freewheel nut breaks free.

My best advice on what NOT to do.... NEGLECT BASIC MAINTENANCE.

Don't think that because you've only had the bike for one season, that all of the cables will be in good shape. My rear brake cable had an awful lot of drag. For about $3 per cable, I think I'll start replacing them once a year. Actually I've already started this winter.