Quoted from ArgosySK:2. Read https://pinside.com/pinball/forum/topic/em-pinball-circuits-basics-to-not-so-basic
3. Read http://www.pinrepair.com/em/index.htm
4. Learn to use a multimeter
5. learn to use a soldering iron.
6. Review VID's guide https://pinside.com/pinball/forum/topic/vids-guides-a-pinside-compendium-updated-72015
7. Under favorite topics use "Topics linked to your games". (Someone may have had the same issue).
8. Before you post, read https://pinside.com/pinball/forum/topic/how-to-efficiently-ask-for-pinball-repair-help-em
9. Clean the male side of the jones plugs.
10. Invest in a leaf adjustment tool and Flexstone/Metal contact file.
Come on! I hardly ever end up using a meter!
Nice list.
To add a tip, there are a lot of adjustments built into the EM mechs, be on the lookout! They can either need adjusting, or have just come loose, causing trouble.
Bonus tip... on slings, take the simple mech apart, clean and just bend the switch blades straight (they're usually bent wonky),file the points and adjust, enjoy great EM action!