I run into a lot of people who have no idea how to write workouts for themselves. They either use some workout of the month from a magazine and jump around, or just have no idea how to organize an effective workout.
I'll address the "Workout of the Month" club. These guys are great. You know who you are. You jump from workout to workout and complain about a complete lack of any progress. You pick a workout that's cleverly titled, "Up Your Bench 240% in 30 Days" or "So and So's 12 week Squat cure". That's great. But, what do you do next? Stop making this mistake.
If you are dead set on following a program, choose one that isn't 12 weeks long. Choose one that you can use for a few years, if not the rest of your training career. Seriously! If you find something that works, why in the name of all that is holy, would you change? It worked for a reason. Just because you use it for 2 or 3 years doesn't mean you should change. Keep using it! Good programs will explain how to tweak things as you progress. Even as you make slight changes, the basics of the program stay intact.
This is why Westside is so successful. This is why Jim Wendler's 5/3/1 is so successful. Look at Bigger, Faster, Stronger and Bill Starr's 5x5. They all work incredibly well. They're all very simple and allow for slight changes as you progress. You don't have to do a new program if you're in the off-season. You don't have to do different exercises for a change. You can adjust set and rep schemes to allow you to achieve your desired goals of each training cycle. But, the basic program stays the same.
Now, if you're a programmer and you enjoy writing workouts, this is where you can really learn to make progress. One of the best pieces of advice I can give you on this is to be patient. You can't write a great program right out of the gate. It will take time to develope. You have to figure out what your rules of training are. This will take some thinking on your part. What are your rules that every workout should have? They don't have to be crazy and you don't need a laundry list of things.
Again, look at Jim Wendler. His rule is Lift Heavy, Stretch Hard and Run Fast. That's his basic workout template. Everything he does is based around those simple rules.
Come up with what you think is important. Write workouts and try them. If they're not giving you the results you want, tweak it. Don't change it. Make small alterations and then just keep working it. Make slight changes as it evolves. But, don't just scrap it and start from scratch every time you don't get what you want from it. Use your mind.
Look at what you think worked and keep it. Change what you think didn't work. Then go to work. Programs are always fluid. If you look at Westside from 20 years ago, it's drastically different, now. But, what has stayed the same? It's still all based around 3 very simple and basic principles:
The exercises have come and gone. The gimmicks (chains, bands, crazy bells, specialty bars) have evolved, but the same basic principles of Dynamic Effort, Maximal Effort and Repeated Effort have gone unchanged. This is something that you need to figure out for yurself. Don't make your training just a physical journey. Make it a mental one, as well. This is how you will truly learn what works and what doesn't.
Use that gray matter between your ears to figure out your own little training program. Make sure it follows a few certain guidelines. Remember, if your program revolves around these movements:
then you're gong to be fine. It's up to you to figure out how you want to put them together and how you want to track them. Don't be afraid to read other people's programs that are very well established. Look at exercise selection. Look at frequency of movements. Look at set and rep schemes. Use ideas that are already proven to work and morph them into your own basic plan.
A note: Don't use a lot of different programs all smashed into one. Rather, take little bits and pieces from them and place them where they fit in your program. If you have your basic template, you can just fill in the blanks as you go.
Here's an example of my basic template that I train clients with.
To elaborate a bit:
Strength (20-25 minutes)
-Lower or Upper 4-5 sets of 3-5 reps
-Upper or Lower 4 sets of 8-12 reps
Metabolic Conditioning (25-30 minutes)
For clients I always do 5-7 minutes of Ab Work because I know they think this is how it should be done. I make it all work.
I use these 3 ideas to put together client workouts. It's nothing earth-shattering. Just some sound, simple programming that gets the job done.
I also use 5/3/1 and use the assistance work I feel I need in order to prep for a meet.