The left hemisphere of the brain is in charge of logical thinking. It is the detail oriented half of the brain---it keeps track of information, recognizes patterns and understands language and the relationship between numbers. This analytical half of the brain processes thought in a step-by-step manner, and exercising it regularly can improve functioning and boost overall brain processes. Brain exercises that involve the usage of words, numbers, reasoning or step-by-step processes can strengthen the brain by building neural connections in the brain, and result in the development of more finely tuned problem solving skills.
Crossword puzzles and number puzzles like Sudoko are considered brain conditioning exercises, and can give the creative side of your brain a short break. Not only can these activities give you a left-brain workout, but also working out a quick puzzle can improve your mood and refresh the more creative, right side of your brain.
If most of the reading you do tends to be skimming stories and snippets on the web, aim for reading something that grabs your attention for a longer period of time. Jumping into an epic novel isn't necessary; reading a full-length magazine or newspaper article is sufficient---as long as you focus on truly reading the article instead of skimming to get to the important parts.
Making daily journal entries is an excellent left brain workout---it's simple to do, and allows you to keep a record of important events in your life. Keeping a diary isn't something everyone finds enjoyable, but you can also spend some time writing in ways that you may not recognize. If you enjoy social networking websites, you'll be happy to know that posting to your Facebook page or Twitter account is another good way to get some writing in on a regular basis.
Learning something new can give the left side of your brain a workout, particularly if the new skill you're attempting to master forces you to use some deductive reasoning. Studying a new language is one good way to do this, but so is following the directions when assembling a piece of furniture or repairing something around the house.