Try spinning the wheel to make sure the tire is seated evenly and not twisted in spots. If it s a rear wheel, make sure the chain is lined-up properly on the cogs. Mount the wheel and tighten the wheel quick-release lever or the mounting bolts. Spin the wheel to make sure the wheel is centered in the brakes. A screwdriver can easily puncture the tube.
Tools make it much easier to pinch the tube and put new holes in it.
Sometimes the valve will leak. If you use the type of valves that cars use, you may be able to replace the valve. Check at a car shop for replacements. This is usually not repairable. You will have to replace the tube.