A number of soft woods aren't conducive to stained finishes. To help even out the color when working with new, bare woods such as pine, fir, maple and birch, try using a pre-stain wood conditioner. These conditioners are designed to penetrate into the wood and allow the stain to absorb more evenly when it is applied later.
Before applying the pre-stain wood conditioner, be certain that all blemishes have been addressed and all surfaces have been properly sanded.
Try to always finish with a light hand sanding, for a perfect final touch.
Remove all sawdust with a shop vacuum and wipe the project with a dry cloth. Then, use a tack cloth to clean off any remaining sawdust.
Use a brush or cloth to apply a liberal coat of the pre-stain conditioner to all surfaces of your woodworking project. As with stain, always work in the direction of the grain. Allow the conditioner to penetrate the wood for 5 to 15 minutes, and then wipe off any excess. As per the instructions on the can, you'll likely be advised to apply the stain within two hours of the application of the conditioner. If the stock appears to be excessively absorbent, a second coat of conditioner may be advisable. Cleanup is with mineral spirits or paint thinner.
TIP: Using a pre-stain wood conditioner will likely lighten the color of your stain somewhat, so be sure to test the stain on an inconspicuous spot on the project.
You may find that you need to apply a second coat of stain to reach the desired color, but the stain's color will be much more even than if you had skipped the conditioner.