As LJ said, no substitute for going to clinics. Listen, try the things they present/suggest. When you get conflicting or significantly differing opinions/suggestions, try everything and use what works best for you, or what you know your coordinator, or potential coordinator, prefers. An example is signaling First Down to the R. Some coordinators may be OK with a ‘big’ or flamboyant signal (like the ‘scorpion’s tail’ point over the head), whereas, I know at least one Power 5 coordinator that specifically does not want flashy first down signals - just an easy and simple point with the hand at the chest.
I highly recommend using a shuffle and/or crossover step for your sideline movement, keeping your body ‘open’ to the play (chest parallel to the sideline) as long as possible. Walking along the sideline, looking over the shoulder onto the field really looks lazy. (Watch NFL LJ Tim Podraza from San Diego; about the best example of staying open to the play.)
Always know where is the line-to-gain, and be really good at getting the clock stopped when there is a new first down. And, be the crew-saver with the clock. As often as possible, check the clock when the ball becomes dead, and step in when the clock needs to be re-set.
Those are highly noticeable things that coordinators can see.
Robert
