Even if the nearest thing to a workshop in your house is a kitchen drawer jammed with assorted tools, it's certain you own at least one, and probably, several screwdrivers.
More than any other tool, a screwdriver is used in many ways for which it was not intended, probably most often for prying, which is why the blade tip is usually damaged. One way to keep screwdrivers in good shape is to set one aside for poking, lifting, opening, etc., and reserve the rest for tightening and loosening screws.
An excellent reason for having more than one screwdriver is that the wood into which the screw is being driven is likely to be damaged if the tip of the screwdriver is too small or too large, not to mention the probability of marring the screw-head slot. If the latter occurs, you may not be able to drive in the screw and may have to remove it with pliers. You should always make sure that the tip is square. If it isn't, you can put it in a vise and file the tip until it is square.
You tighten a screw by turning it clockwise. You loosen it by turning it counterclockwise. There is one exception; when a screw resists removal, and you give it a quick turn clockwise before turning it counterclockwise, it will yield.
If a screw has a head with a cross-shaped slot, you need a Phillips screwdriver. It has a star-shaped point that fits the slot of that type of screw.