The greatest challenge in achieving this, is that there is no 'best' session, nor is there any way to determine if there ever was. That said, there are better and worse ways of designing programmes.
With that in mind, the following list of 'rules' should get you somewhere in the theoretical 'best' ballpark.
Warm Up Properly
This is a bug bear for me as I see very few people warming up effectively. Most people lob weights on a bear and go at it, or spend five minutes on a treadmill before their chest workout. A good warm up should meet the following requirements:
- Progressively establish active range of motion at the joints to be used in the training session
- Progressively establish working load on the muscles to be used in the training session
- Progressively increase activation of the central nervous system relative to the activity scheduled for the training session
If you achieve these, all the other 'stuff' (raised heart rate, temperature, synovial fluid viscosity, psychological readiness, etc.) will be fine. BUT, you can achieve that 'stuff', without hitting the big three listed above.
Do the most important exercises first or second
When I studied with legendary strength coach Ian King, he always said that whatever you do first, you do best. Therefore his recommendation was to put the most important exercise first in the session. Whilst I'm certainly not going to disagree with him, many, if not most, of his clients are elite athletes and therefore different from the average Joe/Jane. Some people need some help getting the most out of their main exercise and often some movement drills or activation exercises up front can really help their technique. Likewise, older athletes may find that a pre-exhaust approach, allows them to get a comparable level of effort on the main exercise with reduced loads, thereby potentially reducing unnecessary wear and tear.
Make your client feel like a star
Another well renowned strength coach, Dan John, has a very simple rule: Never make the client look or feel like an idiot. Always make sure you choose exercises the client can do well (or at least well enough). That doesn't mean don't push them outside their comfort zone, just that they should feel successful after every workout, not like a klutz.
Program to the goal
One exercise I like to run when delivering courses, is to have learners write out a program based on a specific client. They then have to try and work out what the main objectives of each others programs are, by looking at the way they've been designed. If I read a program, I should be able to work out very quickly what it's designed to do. For example, if the goal is fat loss, spending 45 minutes on corrective exercises and breathing drills is an ineffective use of time. Likewise, if you want to get fitter, I'm not going to give you a powerlifting 5x5 program, as whilst it may have benefits, they're not directly relevant to your goal.
Monitor constantly, but only change when necessary
The two reasons that people don't get the results they want are program hopping and doing the same program for too long. Most programs are designed for 4-6 weeks of progress, if a program seems to not be working at week 2, try and determine why and then address it in the next phase. But complete the planned 4-6 weeks regardless. Some clients take a little longer to get started than others, changing the program too often means they never really get traction with it. Likewise, most people will have got the bulk of their adaptations within 4-6 weeks tops (less for more advanced individuals/athletes, more for newcomers). Additionally, no matter how exciting the program is, it'll start to get boring after a while. Changing it keeps the client interested.
Factor in evaluations
I love assessments; they let me know how a client's progressing. That said, not all of them are formal assessments, some are workouts or complexes. One of the qualities I like about Crossfit, is it's use of WOD's as a measurement, i.e. "I did Fran today and managed to knock 30 seconds off my personal best". Having some 'go to' workouts you know well enough to set performance benchmarks for is really helpful. Additionally, more formal assessments or tests are equally valuable, especially if they help demonstrate to the client that all their hard work is moving them closer to their goal.
Keep the client happy.
The client is paying you for a service and it's up to you to provide it. In some cases that just means being a reason for them to make it to the gym, in others, helping them achieve a performance outcome. Regardless, remember to never lose sight of what that person is there for. This often gets neglected when their training wishes contrast with our training philosophies (I'm never programming boogie bounce into a workout).
Keep it fun.
As fitness professionals, we can sometimes take exercise and exercise science a little too seriously. Few clients will share our enthusiasm for lever lengths and strength curves, (although don't you love those who do). Make sure you include something in each session that makes the client laugh or smile. Energetic plays such as Animal Flow, Calisthenics or Tumbling are great for this and can be a great way of improving movement, balance and coordination.
There's no such thing as the 'perfect session', but if you stick to the guidelines listed above, you'll come pretty close, move your clients closer to their goals and keep them happy along the way.