The more you practise the better you become. Start off with 15-20 minutes sessions morning and evening. Sometimes starting off with a mantra will help you focus. Visualise energy being drawn from your root charkra through to your third eye (ashna centre) and release the mantra through the third eye...keep repeating the cycle. Say the mantra out loud if you can and go softer and softer over about 10-20 minutes. I really recommend you be patient and perservere with meditation, it is well worth it.
The best teacher is yourself only. Try to meditate for five minutes atleast 2-3 times a day. See the changes going through your surroundings when you are meditating. Try a new technique everyday you'll get adapt to it.