Attempts to remove a tight screw can often ruin the slot. If the head is above the surface, use a hacksaw to cut a new groove at a right angle to the original slot. Exert pressure evenly, not jerkily, with a screwdriver to ease out the screw.
Or remove the screw by gripping the head with locking-grip pliers.
Where a slot is ruined and you can't get a grip on the screw head, guess the size of screw shank and select a twist drill of the same size. Insert this into a power drill and use it to drill the head of the screw. Eventually the head will drop away. Remove any fitting, then turn out the screw shank with a mole grip. But be warned; there are some modern case-hardened screws which cannot be drilled out in this way.
If a screw has rusted in place, try applying the tip of a hot soldering iron to the head. The heat will expand the screw head and may loosen the rust. Or try easing oil around the screw.
Screwfix is the UK's largest direct and online supplier of trade tools, accessories and hardware products. To view their range of screws customers can visit the website here: http://www.screwfix.com/c/screws-nails-fixings/screws/cat840008.
