I found this nice article at a website. It was a really useful article. The following is the link to the website:
http://www.luggagebase.com/repair_tips.aspx

Many problems require a luggage repair station to rectify but here are a few repairs most anyone can perform*:

• Metal zipper is hard to zip - Use wax stick and rub along both sides of the zipper teeth.

• Coil Zipper (Common zippers used today) separated - Most are self repairing. Just forcefully push the zipper slide back to the very start position. If it easily separates every time you use the zipper then use a pair of pliers on a wide setting and lightly squeeze both sides of the zipper pull but do not clamp down on the tab or where the tap and slide connect. (View Image)
• Hard side luggage has a dent - Most hard side luggage that has a dent is usually made of ABS and can be repaired. Manufacturers like Samsonite commonly use ABS in manufacturing luggage. Use a high wattage hair dryer, 1600w or higher, to heat up the area where the dent is. Takes approximately 15 minutes in most cases. DO NOT USE A HAMMER!!! When the ABS heats up, it will reshape itself to the original position. The hair dryer technique also can be used to repair white stress marks.

• Hard side luggage crack – ABS shells only – First follow step #3 if it is also dented. Apply an ABS compound, found at your local hardware store, to the crack on both sides of the shell and let it sit overnight. Repeat for added layered strength.

• Combination lock stuck – This is usually the result of the combination being changed by accident. There are 2 techniques: A.) Under good lighting, try to see the tumbler (the metal action underneath the wheel) by looking down the crack between the wheel and the lock casing. While turning the wheel, notice any flat area or notch. That will either be the number for that wheel or you may have to go 5 digits from that number. B) Uses the same technique accept that you use the corner of a thin piece of metal (like copper sheeting) down the crack to feel the tumbler.

• Wheels – While most wheel repairs must be done by an authorized repair station, there are some manufactures that have consumer friendly wheels that anyone can replace. Most of Travelpro luggage uses a screw-and-bolt construction that allows the customer to replace a wheel using a normal screwdriver. Swiss Army brand Victorinox also uses this feature on their wheels but using a hex screwdriver or Allen wrench.

• Handle system is difficult to operate- This may serious or it may not. Try using WD40 or Vaseline on the tubing of the handle system. If you notice rubbing or warn marks on the tubing, it may be slightly bent. Although not recommended, you may try to bend it back yourself**. Be very careful and only do it slightly (Better too little than too much). Too hard and you'll make the problem worse. Try to align the worn mark on the tubing to the entry point before putting pressure on the handle. 80% of them will need to bend away from the case (Back). **Not recommended for novices.