Class Echo airspace: controlled, but no clearance to enter VFR
To enter
None for VFR — but it is where IFR traffic operates, so use advisories.
What it is
Class E is controlled airspace that is not B, C, or D. As a VFR pilot you do not need to talk to anyone to fly in it, but IFR traffic is being separated here, so flight following is smart.
Radio etiquette
There is no entry call, but requesting VFR flight following gets you traffic advisories in Class E and a controller watching your route.
Surface-area Class E
Some non-towered airports have Class E to the surface for instrument approaches. In low weather you may need a Special VFR clearance to operate there — and you must request it.