Ball skills: I have always seen this as a 360 degree skill with multiple loops for the better skilled player. Always in connection with the basics and then finding the correct application.
Example : many can perform perfect cuts verse cones but they forget to sell the feint.
Mentality: Develop a sense of honor in being a footballer. Try not to do the old tired cliche "No one cares about soccer".
Find what works for your team. The captain on my team is 1/4 Japanese and I am a fan of Miyamoto Musashi so it has been fun using some of his teachings.
"The warrior enters the field of battle without ever leaving" not Musashi word for word but along the same mental idea.
Success vs Winning: Talk to the team and find your objectives.
Start with individual objectives ( crosses from the side of the 18, headers for goals) all these individual ones will actually require a team effort.If you complete enough successful objectives you will win.
Stay in contact with your JV and Varsity coach and keep some continuity. Develop the "One Program" mindset.
Retention: Give yourself the opportunity to coach at younger age levels. The need for the better coaches at younger levels is greater than experienced coaches at the upper levels. The younger kids get a kick out having a High School coach, they feel like they are getting professional training.
The above has so far worked out fairly well with our program. Our JV started with borrowed equipment and volunteer coaches, we had two 8th grade players as de facto coaches.
Using the Coach Chass/Shiner yardstick we have completed some objectives and still have many more to go, Ooh Rah!