One of the worst advice you can get about meditation is that in order to reap any benefits one must meditate for a long period at a time. Well this simply is not true. The fact is that meditation can benefit anyone even if they only spend few minutes each day sitting silently and counting their breath.
Our mind lost its ability to concentrate on a single task for a long period of time due to constant interruptions and multitasking nature of our modern world. Simply sitting down and paying attention on our breath without thinking of thousand things is extremely hard, especially for a novice meditator. And like anything you must start from the very beginning and continue practiceing in order to improve and build your meditation practice. That's why many people stop practicing only after few times they try. They start with 15-20 minutes and after completely failing, they simply give up.
"A journey of a thousand miles must begin with a single step." - Lao Tzu
If you never meditated before, starting with even 5 minutes a day will be a good way to start. Bue even this short meditation practice done on a daily bais will make you realize how beneficial meditation can be in reducing stress, making you more focused and just making you feel better mentally and spiritually overall.
So start with few minutes a day and as you get better and are able to stay focused more and more, slowly increase your time and continue to practice on a continual basis, preferabley every day and just like with anything, you will get better and meditation will become an essential part of your daily routine. It has for me.
If you're looking for a good source to get you started, here is an excellent book that will help you get started.
5 minute meditation video