#2: One of the biggest hurdles I had to overcome as a new player was being able to judge just how big an army I needed to take an opposing army without going over. It's very common to pile several turns worth of unit production into a giant unstoppable army and march around with just 1 or 2 of these armies against the AI. However, it's significantly more efficient to march around with 3-5 armies that are "just good enough" to defeat the independents without losses.
Choosing which independents to attack is also important. Ideally you want your starting army to take out the provinces that are "just weak enough" to defeat without losses. You want to leave the really weak provinces for an expansion army. You will probably have to combine your starting army with an expansion army to take the strongest provinces, so you want to make sure that the individual armies have done as much as they can do on their own first.
#4: I agree that most provinces only need level 2 or 3 site searching. Acashic Record is awesome because it provides "certainty" that you've found everything, but it's too expensive to be worthwhile in most cases. One thing that might help is knowing that certain terrain types like swamps have a greater chance of having magic sites while farmland has a lower chance. Another thing is if you find a province with unrest, or heat, or fortune and it doesn't appear to be related to your or someone else's dominion. That's a big clue that a site is there. Overall though, do the best you can but don't waste too much effort site searching unless you are desperate for a certain type of gems. You can always conquer the provinces that your opponents have site searched.
On the flip side though, some sites can win the entire game by themselves. These can be sites that allow you to recruit powerful mages in a path your nation doesn't have naturally, but are usually sites with something like "Blood Bonus: 20%". Basically it reduces the cost of all blood spells by 20%, meaning all your summons are cheaper than everyone elses. There are similar sites for Alteration, Construction, etc. If you find one of these sites, build a castle there, and defend it like it's your 2nd capital. So site searching can be a delicate balance.
