One light flickering and several rooms brightening or dimming together are different descriptions. Neither tells you the cause on its own.
The issue can involve lighting equipment, the home's wiring or the incoming supply. ESFI lists flickering and dimming among electrical warning signs, so don't dismiss a persistent change because the lights still work.
Tell the electrician which rooms or fixtures are affected, whether they change together and when it started. Mention a recent lighting change, electrical work or outage.
If it seems connected with an appliance starting, report that. Don't keep operating the appliance to reproduce it.
A short video from an ordinary occupied area can help show an intermittent problem if it's safe to record. It doesn't require opening equipment or approaching the service connection.
NV Energy's help information includes reporting dim, flickering and partial power conditions. Use its official contact channels and describe what's happening.
Contacting the utility doesn't establish that its equipment caused the issue. An electrician may also need to check the house. Keep the utility's response so the electrician knows what has been reported or checked.
Don't approach the meter, service connection or a damaged line to decide whose equipment is involved.
A quote should explain what the electrician found and which fixture, circuit or service related work is proposed. “Fix flicker” doesn't tell you that.
If the recommendation is broader than expected, ask why the additional work is needed and what the inspection couldn't determine. Separate a repair for the reported fault from an optional improvement offered at the same appointment.
Get any agreed change to the original work and price recorded in writing. The change order guide explains what to include.
For smoke, fire or immediate danger, move away and call 911. Tell the responder about a burning smell, sparks or abnormal noise. Don't touch electrical equipment to check whether it's hot.
For a routine appointment, the existing observations, utility response and recent work history give the electrician a useful starting point.