Don't forget to eat your protein

Protein is the building block for lean muscle, if your body doesn’t get enough protein your body cannot repair itself properly after your hard training session. As a general rule of thumb 1 gram of protein per pound of body weight is a good starting point to ensure you are getting your required protein.
Allowing the body a near constant stream of amino acids in the blood is key to keeping the body in a anabolic (muscle building) state. This means having a source of protein with each meal.
Protein is especially important after a hard training session, whey protein drinks are a great option, as it provides easy to metabolise protein that can be consumed straight after, or very close to, the end of a training session.
Great sources of protein include: whey protein drinks, egg (or egg substitutes), meat (beef, pork), poultry (chicken, turkey), seafood, soy protein and quinoa.

Do your squats

Exercises that train more than one muscle give you the biggest benefit when you are trying to build muscle and get stronger. Squats, deadlifts, pullups, pressing movements and definitely thrusters are great compound movements that should be done regularly and will provide added benefit if added into an open gym training session a couple of times a week.
Research has shown that the body responds to multi-joint, compound movements, like squats, by increasing secretion of testosterone and human growth hormone which helps to build muscle.

Don't scale your workouts too far

Choosing the option to make a workout less taxing and less fatiguing is a slippery slope. Getting comfortable and not pushing the boundaries while you are at the gym will result in less adaption needed by the body and therefore fewer increases in ability or strength. Constantly scaling movements like pullups will not progress you to being able to do pullups unaided.
Doing the hardest version of the exercise appropriate to you and constantly pushing yourself will yield the best results for your body.
This does not mean workout outside your abilities or in an unsafe manner. It means choosing weights, movements and scales that are going to challenge you the most. Don’t chose a weight because it will make the workout faster, or because it is the weight you always do.
Always try to improve or progress your movements, don’t be satisfied with the scale you currently do- work towards RX!

Long metcons every day will not make you stronger

For a muscle to develop and grow it must be overloaded and then given recovery time to adapt and grow. Going to the gym every day and doing metcons over 20 minutes long with light weights and high reps will not create bigger stronger muscles.
Avoiding rest days will also be a detriment to any adaption made by your body. When you train you fatigue and work the muscles, tearing the tissue, when the tissue is repaired the muscle grows bigger and stronger. For this to happen you must give the muscle time to repair. While sleep is essential for this, as well as for your overall health and wellbeing, sleep alone is not enough. Your body needs recovery days.
To get stronger you must follow techniques that focus on muscle growth- for example: slow eccentric training, training at maximal loads for low reps, dynamic and ballistic training (explosive or plyometric movements like box jumps). These movements should be done at the start of a training session when you are fresh and can put 100% effort into them.

Don't be afraid to fail

When you are doing your strength sessions it is important to work to failure when the situation calls for it. When building to a 1rm (or 3 or 5) then you are being asked to fail. Without failing a weight you cannot know what your maximal lift is. Stopping when it “feels heavy” isn’t going to get the job done.
Training to failure is not always necessary, especially on compound movements, and if overused can have a negative impact on training and overtax the central nervous system. For single joint movements training to failure can be done for frequently (eg: bicep curls).