Customers can be divided into those who understand the costs of running a business, and those who don't.
You want to focus on those who do understand, and are happy to pay the going rate without quibbling. As mentioned in another recent thread, it can help to be flexible such as being prepared to work the odd evening or weekend, if that is all that is convenient for the customer.
You want to avoid those don't understand and think £40 or even £30 an hour is expensive. They are often getting several quotes and trying to play one off against the other, or even fishing for information so they can do the job themselves. I think social media can attract more of this type of customer.
It took me 2 years to go from nothing to a decent turnover that I was happy with. I used leaflet drops early on (first 2 years) with someone reliable who combined maybe 6 leaflets (but none competing) and was selective about the areas covered.
I know some people have good success with entries in local/community newletters/ magazines. But beware of people phoning you up offering you the only electrician's place in some local directory that most people don't know exists and hardly anyone will see.
You can get free basic entries in various online directories but they then usually try and sell you expensive premium entries or advertising, which I always regarded as a waste of money.
I have a basic web site, more as a presence if people want to look, helps show I'm a genuine business etc. It does bring a few enquiries, but it also brings lots of spam from people promising to get me a top google ranking or whatever if I bung them a lot of money.
As always, word of mouth recommendation is the best source of new work. I often do small jobs that come as a referral becuase they can lead to more work.
Oh, and avoid like the plague anyone who wants money upfront to give to X number of emergency call outs or EICRs a month, they will turn out to be a scam.