Assuming you're talking about a road bike, here are a few things you should do to get it ready for spring:
1. Check your tires. After a winter of riding on salt-covered roads, your tires are likely in need of some TLC. Check for cracks and bald spots, and inflate them to the correct pressure.
2. Lubricate your drivetrain. A dirty drivetrain will not only make shifting gears more difficult, but it will also shorten the lifespan of your components. Use a degreaser to clean everything, then apply fresh lubricant to your chain and derailleurs.
3. Inspect your brakes. Brakes pads wear down over time, so it's important to check them regularly (especially if you've been riding in wet or icy conditions). If they're excessively worn, replace them with new ones. While you're at it, take a look at your brake cables and housing to see if they need to be replaced as well.
4. Tune up your suspension fork and shock(if applicable). Over time, suspension forks and shocks can lose their effectiveness due to normal wear and tear - meaning that your ride won't be as smooth as it once was. To prolong the life of your suspension components, have them serviced by a professional every few years (or sooner if you ride frequently).
5. Clean everything! Mud, grime and salt can build up on your frame over winter, so give everything a good wash (including removing the wheels) using soap and water before lubing anything up again..