What he doesn't talk about is how he decides he wants suspended chords, and how he chooses several in a row that work well together without even thinking about it.

This is where an understanding of music theory really comes in handy. It takes much of the guessing work out of how to work out a progression. And it doesn't have to be an extensive, 4 year kind of understanding either.

Listening to plenty of other tracks and studying what is where will help illustrate why certain chords fall in certain places. For me it all comes down to tension and release, which is how a piece of music conveys grow or direction. So, taking the suspended chord as a example, this can often happen right before a cadence because the suspension raises the tension which makes the cadence (release) that much more satisfying. Harmony is just one of many methods to create tension and release.

I really like what Jeff Coffin suggested when discussing critical listening: listen to a full song and zeroing in on only one track at a time. Toggle this with listening to the track as a whole and you'll start to see how everything is combined to make a good track.

Obviously if you stick to one key you can't go far wrong harmonically, but without some extra sense of purpose or direction you're unlikely to come out with anything compelling in terms of tension and resolution or melodic flow either.

In my opinion, you CAN stick to one key and create a sense of purpose and/or direction. But it does mean you have to be more intention about what chords where, your instrumentation (and it's evolution), as well as the voicings you picked. Then add in articulations and dynamics and you have so much to pull from. Something that Billy Joel does, and he learned it from the masters of classical music I believe, is a inversion chord cadence vs. a root position cadence. Such a simple, small change but it can really make a difference between a somewhat firm and very solid cadence in a song.

Sure, throwing in a suspension here and there helps if I can resolve by step to the next chord - but I have no instinctive way of knowing where to place them short of playing random chords in the key until one sounds good. I'm not comfortable with that.

Some of my more interesting work has resulted from an element of randomness. Don't worry too much about happy accidents.

So many good ideas in this thread! I definitely agree with:

1) "borrow" material and incorporate it into your own songs/practice as a way of learning the language more. Jazz and rock musicians do this by learning "standard" licks early on in all 12 keys and then incorporating it into their own music. It doesn't mean you regurgitate the licks 100% each time. Instead, after much practicing they begin to evolve into your own speech pattern. Many legends got their start from listening and then transcribing (be it just by playing along with by ear and/or actually using pencil and paper) the musicians that inspired them. They were teaching themselves the language of music.

2) Learn the rules. Then learn how and when to break them. Do what feels nature to YOU as a composer, while always striving to find your own touch or voice. At first glance these seems like a contrary statement but you have to first learn the words, phrases and overall language of music before you can really speak it. This doesn't have to happen with theory text books and formal classes but almost always happen with at least critical listening and the borrowing step from above.

Whenever I've felt like I'm running into a rut in my compositions I try a few things to stretch myself - take on a completely new style. Work with a completely new set of instruments/samples. Write in a key or mode that isn't normal for me. Write at drastically different tempos - really slow and really fast. Try different time signatures. Anything that can add a new element for experimentation and change. See how that changes what ideas you come up with.

I'm going to throw out few things not mentioned here, some may sound bizarre in some cases but when you're stuck in a rut, they may help you, as they help me a lot when I find I can't get the ball rolling with my compositions.

Record your jams

This might sound pretty obvious in other cases of composing (such as band work) yet many people don't take this wonderos tip into consideration when trying to come up with a new tune for their next musical project. I often open up my DAW, in this case, Pro Tools, get a couple of nice sounding instruments set up, hit record and just jam or improvise over some very basic chord structures, the amount of times I hear people say something a long the lines of "I came up with a cool melody, but now I can't remember it" is quite a lot, me included, so remember to hit record whilst jamming something out as you may discover an super catchy melody accidentally.

Set yourself a challenge

A strange yet useful tip to get yourself out of your comfort zone and into uncharted territory that you've yet to discover yourself, is to set yourself a challenge. Be it timed, themed or something else that limits you to staying out of what you know can help you in progressing through various styles of playing. Here's an example of something I did a few weeks ago. I gave myself a time limit of 1 hour to complete a 30 second composition with the theme of 'futuristic'. I actually surprised myself with the results, as I and I'm sure a lot of people work better under pressure (which the time limit gave) and come up with 'out of the box' ideas.

Use the MIDI Editor to manually input notes
A common routine people seem to find themselves in is only using external devices, such as midi keyboards, to come up with chord progressions and melodies/harmonies when in actual fact, even the most talented and knowledgable musician would have a tough time adding in those 64th trills followed buy a chromatic scale running up spanning across a 5 octave range every demi-semi quaver in the tempo of 200bpm. Well the previous example might be a little farfetched but don't be afraid of using the in-DAW MIDI editor to your advantage as you could come up with the most memorable melody by shifting a few notes into different positions from your previous jam or even input chords that you couldn't quite figure out/reach. I admit this is by far the most trial and error technique on here, yet you can come up with some awesome results.

Hope some of these tips helped you out, if you need any other tips/tricks, feel free to PM me. :)