Your pieces being developed doesn't necessarily lend itself to a particular plan. Believe it or not you should have a vague idea of what you want your pieces to do from move five and onwards.
Problems in forming plans.

My question to you would be, how do you know where to develop your pieces, if you don't have a plan? Saying you have your pieces developed but can't think of a plan is a strange combination imo. There are a few ways to think about it during a game. First is to see what your opp is trying to do, and do prophylaxis. Or you can find the weak part of his setup and play against that. You have to establish whether you are attacking, equal, or defending, play accordingly. Plans have a lot to do with pawn structure, so prob taking a gander at 'My System' would be useful.

You said "When I have a slight bit of initiative, my pieces are developed, no tactics are presenting themselves to my feeble mind, and it's my move, I have no clue on how to form a plan." Be patient in these moments. I find that simple 1 or 2 move plans are many times enough until something happens that make things more obvious. If there are no clear targets, or tactical shots, take a few moments and see how you might improve your worst piece. Do you have any weaknesses that you can shore up? Does your opponent have any weaknesses that could be potential targets? Are there any exchanges that will create new weaknesses for him that you can take advantage of? What is your opponents best piece, and can it be traded or made to leave its outpost? If you have the initiative, why is your opponent suffering, and how can you prolong or increase that suffering? These are all good questions to ask that will very likely lead you to simple 1 or 2 move plans that are useful.
If after all this you still can't find a simple plan, then simply look for a move that will NOT make your position worse than it is i.e. making a backwards pawn, or trading your good or most active piece for his bad, inactive one etc.
I read in annotation and books about plans to "take control of a " or similar ideas, or even innocuous moves that somehow begin to generate an attack! Yet, I find myself often unable to put these ideas into my own play. Is there any trick to it, or will it just come with enough experience and study?
I'm no expert by any stretch of the imagination, but I think this comes with experience and knowledge of certain positions and how to handle them. Sometimes I tend to get really impatient when I can't figure out a plan too, and many times do something dumb trying to force something that ain't there. I have learned that if I have an advantage, and just don't do anything stupid to lose that advantage, my opponent will eventually do something dumb himself. It's funny how that works. To know your own weakness, and being careful about it, you will see your opponents making the same errors you used to....lol
Anyhow, hope this helps a little. Good luck!

Thank you so much for your responses! Playing for little gains or to improve your position seems like sound advice, and I'll put it into practice in the match we have today. The length of this post seems inadequate to thank the people who gave such a great deal of useful advice, so again, thank you!

Sorry for the double post, but I finally managed to form a plan and win a game on the first board! Take a peek here:
http://www.chess.com/forum/view/game-showcase/first-win-on-first-board
Shameless self promotion aside, it's only been one day but taking a fresh mindset on the game has really helped with time issues and headaches. Thanks again!
I have a specific problem. I know my endgames for my level, at the very least, and my tactics. Because of the awkward way I started my journey into chess, I even know my opening theory. My problem lies in forming a plan. When I have a slight bit of initiative, my pieces are developed, no tactics are presenting themselves to my feeble mind, and it's my move, I have no clue on how to form a plan.
I read in annotation and books about plans to "take control of a <square that is good to have in this position>" or similar ideas, or even innocuous moves that somehow begin to generate an attack! Yet, I find myself often unable to put these ideas into my own play. Is there any trick to it, or will it just come with enough experience and study?