keyboard access

Is there a standard for keyboard activation of drop-down menus? We are using multiple drop-down menus from various sources which behave differently from one another. Technically speaking, each individual jump menu is WCAG 2.0 AA accessible because it can be navigated keyboard-only, but the technique for opening the menu varies from menu to menu.

I can't imagine that to be a pleasant experience for site visitors, but I also can't seem to find documentation from an authoritative source for a standard menu-open behavior that could (theoretically) be applied across all drop-down menus.

Is there a standard? Where is it documented? If there is no standard, is there a way to force a single behavior across incompatible drop-downs or else enable forgiving actions? If not, is there a reasonable way, e.g., through appropriate ARIA labeling, to communicate the correct way to access a particular drop-down menu without forcing the site visitor to figure it out for themselves?

I despair of keyboard-only visitors being able to achieve mastery of drop-down menus on websites.

Details follow:

This issue cropped up recently (I am not sure if it has been discussed elsewhere or even resolved). If it has please let me know. With the advent of version 6 a couple of my vision impaired friends have told me they find it much more difficult to use blocks in version 6. This has resulted in some of them going back to using version 5.*. This issue concerns the keyboard accessibility of blocks. i believe there has been a move towards a "drag and drop" model with blocks when re-ordering page content.