For Practice: it is best to leave it as is for both position and formation, especially position where you should always have what you believe to be the most effective distribution for each particular position. There are some who alternate how much time is spent on a certain category for a position such as TE where virtually every skill should be practiced except for kicking and punting. For formations, the same is true, figure out which formations you want your team to focus on and leave it at that. Generally its a minimum of 2 offensive and 2 defensive especially for a beginner. Some coaches run 4 or 5 offensive sets, but don't necessarily practice them all which is ok. As for which formations are practiced - that shouldn't change - but how LONG you spend practicing can change as the year goes on. Some coaches like to start at maybe 10 minutes on a formation, especially if its new to the team, and then after game 6 or 7 go down to 7 minutes and throw those extra 3 minutes into Special teams or even use them to add to the individual practice times. It can vary and you shouldn't be wary about changing to whatever you see fit. For practical purposes GD Support has said that anything less than 6 or 7 minutes practiced for positional skills won't result in much of an increase and will only keep that skill from dropping.

As for your other questions, they are basically the fundamental questions about how GD works, meaning some coaches won't be willing to share their secrets and others may only think they know what works best. The only real answer is to use what the FAQ gives you and use process of elimination to find out what works best for you. For instance in regards to your defending trips that run alot but not always, you could play a conservative run/balanced 4-3 to get an extra DL in the game but have your LB's playing back a little in case of a pass or you could play a Nickel Heavy Run which would give you 6 in the box but closer to the line of scrimmage. Again, you'll get some coaches that think one or both of those options are great or are terrible. but both are logical considering what the FAQ tells you about personnel in each formation and what aggressive/conservative means in terms of defense. As a rule or baseline to work from both in terms of practice time and game play. Start with using the 4-4 as a defense against running formations and a Nickel against passing formations. This is what most coaches start with and continue to use. Mix it up and find out what works best for you and the players you have.

Check out some of the Newbie advice threads in the main forum using the forum search function and also read all of the developer chats under the drop down menu under WIS at the top of this page. good luck.