What was your biggest single aid to improving?

Hi hardydog. I'd say to start learning scales, thats what is helping me get over the plateau. I'm still learning and working on them.

Im basically a strummer and fingerpicker. I am awful at any kind of lead work or scales. But you do have all the time you want to learn. Basically you have only plateaued if you choose to. I may have chosen to.

My #1 improvement method,, find people who support and challenge you, yet help you to improve.  Maybe this is why chordie is so great. and skype jams are not bad either,, but actually being in a room with other players,, this will improve you with out you even realizing it.

The biggest jump in my ability was when I was still in High School.  I played in a basement band with 3 other guys who were older than me, at the time At the time I was still pretty new to guitar.  they showed me a song and what my part was to be,, and we took off.  If I got lost, Mike (lead vox lead guitar) would notice, turn to me and start playing my part and I would follow an get back on track.

So, finding someone to play with is the best in my opinion.  but all the other suggestions are great also. (Iam not big on scales and lead soooo LOLOL)

Just being able to have lots of time on my hands since I retired has done the trick.  I still have a long way to go, but I am slowly getting there. Lots of practice is the key.

I'll echo what BlueJeep said about learning scales, and then just practice and more practice. I've also found it helpful to learn what every fret position is by heart, and a basic fretboard chart like this one is indispensable for that:

http://www.guitar-chord.org/fretboard.html

Whatever tactics or methods are used, there is no substitute for practice. I did have to make a mental adjustment, to not let my many inabilities spoil the enjoyment of playing. If it becomes too tedious or mechanical, the guitar could end up collecting dust somewhere. A good practice session which I find works personally is a 3rd playing well-known favorites to get warmed up with, the next 3rd spent doing scales and exercises, and the final 3rd spent tackling a brand new song or riff. Over time, you will surprise yourself at how much progress has been made in a relatively short time ... that really puts wind in a person's sails!

I've been playing for about 40 years and have probably plateau'd several times, even stopped altogether during some difficult periods. i think watching other peoples techniques and practising as much as you can, and above all keep it fun, because music should always be enjoyable, never a chore. Never take it too seriously.

Hi...I know Im the new dude to the Forum but what helped me and Im still  rather new at Guitar like a yr in,  but Find a Lead Riff that you really want to  master  and get it down and break it down Note  for Note the Key word  here take it  (Slow),My first was the opening  intro  Riff  Dont Fear the Reaper Had to learn it on Acoustic  tho lol Good Luck have Fun....

Mine was discovering and using a capo...opened up so many songs I thought I could never play and sing.

Another thing that has helped me is giving up.  Really.  I gave up caring what people thought about what I was playing and sounding good, and now I'm just having a good time.  Funny thing is, since I gave up worrying what other people think, I've gotten a lot more complements.

Youtube. Without it I wouldn't be playing.

For me it was box patterns.  Everyone knows minor pentatonic box patterns, but there are other "boxes," too. 
Get the muscle memory of a few boxes, and learn the root notes.
Then try to play along with a few songs.  Find out what key it's in, and noodle around in the box.

My next door neighbour approx 2000, Peter Hills R.I.P. In bands from the 60's he could hear a new Beatles song on the radio at work and was able to play it that night in the local pubs and clubs. What a great talent, not only a fantastic musician but also avery funny man. I'm proud to have known him and learnt if only a small amount from him. I bought a guitar after meeting him.
Thanks Peter.