Avoid Seized Snaps
Damaged canvas due to unyielding snaps is nearly always due to neglect. Snaps should be kept clean and lubricated. Wash all your snaps regularly, either with pressure from a nozzle or with a container of fresh water and a toothbrush. A little petroleum jelly or teflon grease smeared around the inside perimeter of the socket half of snaps to lubricate the spring and retard corrosion is sure to extend the life of your canvas.
Freeing Frozen Zippers
Plastic zippers are excellent in the marine environment, but far too many have metal slides. In a damp, salty environment, metal slides invariably corrode, becoming immovable. Don't just keep pulling until you rip the tab off. Soak a couple of cotton balls with white vinegar, pack them onto the top and bottom of the slide, and cover with plastic wrap. Wait. The acidic vinegar will dissolve the oxidation, freeing the slide. Once the zipper is again functional, flush both the slide and zipper with fresh water, dry thoroughly, then give the zipper and slide a liberal application of zipper lubricant. If you remember to flush and dry all metal zipper slides as part of your "putting the boat away" routine, an occasional application of lube should keep them all working smoothly.
Clear Fogged Plastic
There are lots of ways to restore the clarity to fogged plexiglass hatches, windows, and plastic instrument covers, but one of the most foolproof is to purchase an automotive headlamp-restoration kit. These are intended to remove fogging and yellowing from headlamp covers and they can do the same for UV-damaged plastic on your boat. Note that polishing kits will not clear internal crazing.
Forest Fresh
Adding a bit of aromatic cedar wood inside the enclosed areas of your boat adds freshness, repels insects, and retards mildew. You can line a locker with aromatic cedar closet-liner planks, add aromatic cedar blocks to drawers or bins, or just lay an aromatic cedar plank on a shelf. Occasionally you'll need to sand the wood and/or anoint it with real cedar oil to maintain the effect.
Vinyl Protection
Stores, such as Jo-Ann, sell a product called marine vinyl. We've found the "cut to fit" material easy to use (no sewing needed), easy to clean, durable, and inexpensive for use on a boat. We use it to protect our tabletop during daily use, thereby protecting the wood finish. We also cut pieces to fit our overhead hatches. With the hatch closed, the vinyl lies on the screen to block the sun, cooling the boat during hot, sunny weather, and helping our air conditioner to not run as much.