A panel shop that has to ask questions is a panel shop that has stopped work. Most of those questions come from the same small set of omissions.
A numbering convention, applied without exception
Decide device tags and wire numbers before the first page is drawn, and apply them everywhere. Half a set in one convention and half in another is worse than either convention on its own, because now nobody trusts either.
If the customer has a plant standard, use theirs. It costs you an hour and saves their maintenance team years.
Generated cross-references, not typed ones
Contacts and coils must point at each other, and they must stay pointing at each other after a page is inserted. Typed references survive exactly one revision. This is what the tool is for.
The I/O list, complete
Tag, description, module, channel, cable, field device. This is the document that links the electrical design to the PLC program, and it is the one most often delivered half-finished. An incomplete I/O list means the programmer guesses, and a guess that is wrong is found during commissioning.
A terminal list grouped by cable route
Terminals grouped by function look tidy on paper. Terminals grouped by where the cable physically goes are what makes wiring fast and fault-finding possible. Group by route, then order by function within the route.
Panel layout with real dimensions and real duct fill
Draw components at their actual size, including the space needed to open a breaker or pull a fuse. Check duct fill rather than assuming it. A panel that is 90% full on paper is unwireable in practice.
Heat load calculated, cooling sized
Sum the dissipation of drives, power supplies and transformers, compare against the enclosure surface, and size the cooling. Panels that run hot fail in the second summer, which is well outside the warranty conversation you want to have.
Parts list matched to what is available
A parts list specifying components with a twenty-week lead time will hold the build regardless of how good the drawings are. Check availability before the list is issued, and note approved alternatives where they exist.
Hand over the native project
PDFs are for the site file. The customer should also receive the EPLAN project itself, so that the next revision does not have to start by redrawing yours.