Workflow that has held up across a few panel projects:

Diagrams first, CAD second. Draft the sequence of operation as plain numbered steps (step / action / transition) before touching any drawing tool. The single-line diagram then falls out almost mechanically: incoming feeder -> main disconnect -> transformer -> control power -> motor circuits with overload protection.

Tools worth knowing:

• QElectroTech (free, open source). The only FOSS option with a real industrial symbol library (IEC-60617 style), multi-wire schematics, title blocks, and cross-referenced contacts between coils and their contacts. Steeper learning curve, but nothing free comes close for single-line + control schematics.
• EPLAN Electric P8 or AutoCAD Electrical if budget exists. Both do automatic cross-referencing and wire numbering, which is where the real time savings are - manual wire numbers are 80% of drafting pain.
• For sequence diagrams specifically: plain text tables or PlantUML state diagrams. A step/action/transition table communicates more to the controls tech than any fancy graphic, and it translates line-by-line into ladder rungs.

Practical hacks:

• Keep one personal symbol library file and reuse it forever; consistency matters more than the tool.
• Number wires by function (line references like 12.3 = rung 12, wire 3), not sequentially - future you will thank you during troubleshooting.
• Generate the I/O list as a spreadsheet FIRST, then import/draw from it. Every serious tool can work from an imported I/O list; it also becomes your PLC tag list later, so the diagram and code never disagree.