What is the proper order for watching the El Hazard series?
Chronologically by release, it goes:  


The first OVA, El Hazard: The Magnificent World (OVA1, 1995)
The first TV series, El Hazard: The Wanderers (TV1, 1995)
The second OVA, El Hazard 2: The Magnificent World (OVA2, 1997)
The second TV series, El-Hazard: The Alternative World (TV2, 1998) 


The Wanderers TV series (TV1) is of a seperate continuity (basically a retelling of the OVA series, but aimed at a younger demographic) to the two OVAs (OVA1 + OVA2). 

The Alternative World TV series (TV2) is set after the second Magnificent World OVA.

So chronologically by story, it goes:


Magnificent World (OVA1) ⇒ 2. Magnificent World (OVA2) ⇒ 3. Alternative World (TV2) 


⤜ || ...somewhere completely unrelated... || The Wanderers (TV1) ⤛