Do NOT ride your motorcycle with open-toed sandals if you are emotionally attached to your feet. Many different varieties of footwear exist which are specifically designed for motorcycle use.
If properly looked after, a pair of good quality motorcycle boots will last you for many years.
So what makes a good boot?
First of all, see if they have a label to indicate that they meet the required standard. In Europe this should be EN 13634:2002. They may also have a "CE" marking or carry the BSI Kitemark.
Then try them on. It goes without saying that they should be comfortable; however bear in mind you're not going to be using them for hiking! Wearing the right kind of socks is also important. If the boots are too tight, this can impair blood circulation in your feet. You may notice that the left-hand boot has a rubber panel on its top surface; this is to protect the upper surface from scuffing caused by the gear lever.
A decent boot should not only protect the wearer against the elements but provide impact protection for the ankle, instep and shins as well as preventing the foot and ankle from twisting.
Look at how the soles are attached. If they are just glued on, they can be ripped off easily in the event of an accident. Ideally they should be both sewn and glued. The soles should be thick, oil-resistant and have a decent tread pattern to prevent your foot slipping on the road surface when you stop at a traffic light.
The uppers should be abrasion resistant, and if leather, should be at least 2.5mm thick.
Regarding the lining, this should be a "breathable" fabric like Gore-Tex. This allows perspiration vapour to escape without allowing water droplets to enter the boot. The lining should also "wick" away moisture, leaving your feet warm in winter and cool in summer.
How are they fastened? Boots which you just pull on can be pulled off very easily if you come off your motorcycle, leaving your feet unprotected. They should be secured using laces, zips, buckles, velcro straps or a combination of these.
Boots are available in many styles and colours; however bear in mind that unless the lining materials are colourfast, your socks (and maybe even your feet!) are going to turn a different colour!
Buy the best you can afford. Not all boots are waterproof; if you are going to be riding in all weathers, waterproof boots are advisable. A zip at the back will tend to let water in; this is why zips are usually placed on the side.
Having spent your money on a pair of boots which fit nicely and look good, remember to look after them! I clean and treat mine regularly with a waterproofing wax. I can recommend Nikwax.