During the months of February and March cut one to two foot long branches from such shrubs as:
pussy willow, dogwood, forsythia, redbud, plum, cherry, wild crab apple, apple, lilac and wisteria.
You can try tree types but shrubs tend to bloom much easier.
If you wait till March and the buds are starting to swell you'll get faster results.
Cut the branches on the diagonal.
Using a hammer, bruise the ends to allow the branches to soak up the water faster.
Put the branches in a vase and add water. Change the water every few days.