Here's a multi-colored [character evidence chart] I made of the various evidentiary provisions that revolve around character evidence, including bias, impeachment, Johns evidence, etc..
The idea is that you start in the middle by asking for what purpose the evidence is being offered. If it's being offered to prove bias, habit, motive, opportunity, etc. then there are rules to follow (laid out in the appropriate box) but it's not "Character Evidence". It is only character evidence if you're using evidence to establish a trait which will then be used to infer that the witness acted consistently with that trait. For example, he's a liar therefore he lied. He's a thief, therefore he stole.
There are exactly four exceptions to the rule that you can't use Character Evidence to establish that a person acted consistently with a particular trait. Those four exceptions are laid out at the top of the chart and include impeachment. Of course impeachment also includes other things that aren't exceptions to the Character Evidence rule. The only way I could think to unravel the intertwining evidentiary rules was to make the impeachment box a different color but clearly mark it as the fourth exception.
Check it out and let me know if you see a way to improve it.