If you're here reading this, then like me you care a lot more about training to achieve enhanced performance than about just looking a bit better with your clothes off. The two things of course aren't mutually exclusive but they are quite different animals when we look at the best way to achieve either.
Doing what's going to get you faster and stronger isn't always the same as what will get you the most shredded in the quickest time - an often unsustainable result in any case. With that in mind, here are some suggestions on how to structure your strength and conditioning training with the goals of being faster, stronger and more powerful.
I've said before (in my free PDF - 10 tips for S&C) that you NEED a programme. It doesn't have to be a complicated spreadsheet with in built equations and graphs at the end of each phase (go for it if that floats your boat!). My first training logs were hand written note books and I programmed daily or weekly. Nowadays I plan 8-12 weeks at a time so doing it by hand has become redundant - hence my new found love of spreadsheets.
The key points are; have a goal. Reflect that goal in each programme. Do the things you NEED not what you enjoy but leave a little something in here and there to keep you motivated (this could be ending a session with biceps curls or abs for example).
Knowing what you are doing each session helps you stay focused on your long term goals.
Here is an example of training schedules for someone who does their sport 3 times a week and so only has 2-3 sessions for S&C vs athletes that have to do twice a day training to fit in their training volume:
Typically you won't do as much S&C training in a competitive period as you can fit into a pre-season or off season period. There are lots of factors that play into managing your training volume; experience and level, lifestyle (work/sleep/family etc), nutrition and supplementation, injury history and more.
The athlete doing 2 sessions per week has a lot to address within those blocks of training. That doesn't mean they train all the possible strength qualities all the time. Periodisation is the scheduling of different training phases over time so that you can focus on enhancing different qualities at different times, as and when required by your sport. Understanding periodisation can get pretty complicated but there are literally dozens of 'correct' ways to do it. The main thing to remember is; INTENSITY AND VOLUME MUST FLUCTUATE OVER TIME AND HAVE AN INVERSE RELATIONSHIP.
In practice this simply means that you can't just keep adding training volume indefinitely (sets, reps, training sessions) without also changing the loads you are working at (intensity). As training intensity rises you must lower volume - if you don't do this you risk overtraining, injury and burnout.
If you are the time poor athlete who can only fit in one S&C session per week, even out of season, then I would: identify what your sport training already takes care of. Is it largely aerobic? (e.g. distance running) Does it improve your reaction speed and develop muscular power? (e.g. boxing) Once you know what you've got, you can see where to fill the gaps. In both the above examples, relative strength training would fill a need and improve performance.
For those of you who can fit in two per week, I'd still determine what you're missing but now you have options. You could use concentrated blocks of 2 strength sessions per week before doing a block of 2 power sessions per week nearer competition. You could do one strength and one power session each week. I say 'could' rather than 'should' as without seeing and assessing you as an individual I can't make blanket recommendations.
The only 'wrong' answer is to do something that you've tried or been doing for a while with no decent results. Insanity.
Trial and error plays a bigger role in S&C than most would like to admit. Rather than make all your own mistakes and waste training time, look for programmes and systems written by experienced coaches that meet most of your individual needs. Just remember it has to meet your NEEDS not your wants... Be realistic about your available training time and honest about your flaws.