Improving your guitar playing is a never ending road to professional guitar playing. Whether you inspire to be the greatest player that ever lived or just to be good enough to play for your family, improvement is always possible.
One way to improve your guitar playing is to imitate those players who inspired you to play in the first place. It's not unusual for a person to see and hear someone else play an instrument and get that feeling that that's what they would like to try at least. You should always remember back to the first time you heard the instrument played and how it made you feel. Do you still feel that way?
Playing in a school band, church group or just your local garage band is also another excellent way to improve your guitar playing skills. By playing and practicing with others and performing for an audience, you become more conscious of your playing and what your weaknesses truly are. Once you have learned your weaknesses, you can focus your individual practice sessions on those weaknesses and work to improve them.
Most important of all I think is learning to relax. If you're stressed out about your playing, it's time for a break. An hour, 30 minutes, a day, some type of break is required. When you played while stressed out, you are more prone to mistakes or even just self criticism. When you start making more mistakes, you get more stressed about your playing. It's a never ending circle. You need to learn to relax and you need to learn to recognize when you're not relaxed and be disciplined enough to take a break. You will see a vast improvement in your skills as well as more benefit from your practicing once you learn to do this.
Another really important thing to add to your practice and your play is to have fun. Of course, you can't have much fun if you're not relaxed, therefore these two tips go hand in hand. Sometimes just playing around and making up stuff helps with improving your play because while you are having fun, you may make up something that sounds really great and decide to incorporate that into your play.
It's important always to remember basic techniques that you learned at the very beginning of your lessons and playing. Just because you've been playing for years and may be really good at it by now, you still need to be able to go back to the beginning and refresh. Teaching others to play is a great way to keep these techniques fresh in your mind. While refreshing your memory, you are helping another player learn to play and improve their skills. At the same time, you are improving your own skills as a guitar player.