I have a mountain bike that I use on road. I like it better that way
The original made-in-china crappy tires lasted maybe 500 miles before they broke down. Handling sucked, too. I bought a small air pump for the garage and it is a great investment. My new tires have a better rolling resistance on them, and have lasted about 1100 miles. I always make sure to spray down metal parts with WD-40/ dry bike lube, but I ride in the wet sometimes so it may differ for a road bike. Another tip, double check your brakes before each ride, and don't ride the brake or it might warp/overheat. The sub-standard disk brakes on my bike warped, and now they are about to fall off because the disk is bent. It is not fun.
To save weight, don't cut the seatpost, replace parts with ligher weight ones, like adude said. This includes kick stand, water bottle cage, etc.
Be safe!