1 - What distribution are you running? I ask this, because it can change how to start apache from one distribution to another. In Slack, you start it with "apachectl start" while in SuSE you start with "rcapache2 start".
2 - Please, tell us the commands you are typing to start that service and give us a detailed error output of it, otherwise we can't do much.
3 - You can test anytime if apache is running by opening a web-browser and typing "http://localhost". If you get any "congratulations, apache is running", so then it's running
Again, just be as descriptive as possible. Doing so, you will get much more replies for common errors.