I recently left my previous job, and in doing so I was reluctant to engage much with recruitment consultants because my experience in the past has been generally quite negative. This time around I found them easier to deal with.
The main thing to consider is that job seeking is both stressful and time consuming, and you want to prioritise your energy towards actions and people that are most likely to yield success.
Job seeking puts you in quite a strange position where you typically don't really know what's going on with your applications, you feel that you're being judged silently by people you haven't formed an opinion on, and you're on the verge of a big step into the unknown.
It's extremely import to focus your efforts intelligently, because it's very easy to burn out with anxiety during a job search and just decide to stay put in a job where you're not valued, simply because it seems less stressful. That's a good deal for your employer, but not so much for you.
Recruiters are a big part of modern day recruitment, and they come in two forms:
In house recruiters are typically quite uninspiring. I found they would reach out to me on LinkedIn with a fairly generic message telling me I was a great fit and they'd like me to apply for a job with them. I didn't actually respond to a single in-house recruiter during my search, because not a single one of them made me feel the company actually wanted me. They wanted me to put myself in their process so they could evaluate me, just as anyone else is open to doing. That's not really the same thing, and the fact that they contacted me directly but without adding any kind of personal touch left me with a negative impression of a potential employer.
Actual headhunters exist, but most in-house recruiters are not headhunting and it's important to recognise the difference if you are contacted. An invitation to apply for a job doesn't suggest the people in charge of the decision to interview or hire you have any more interest in you than any other company does.
Agency recruiters are an incredibly mixed bunch. There are plenty of scummy recruiters around, and if you feel that one you are dealing with is being dishonest or pushy or in some way not acting in your interests, just drop them. There are also good ones who behave professionally.
If you're on LinkedIn or you post your CV anywhere online, you'll get a deluge of contact from recruiters giving a one-line introduction and asking to phone you. It's perfectly fine to push back and ask for more details on opportunities before giving out your phone number. A typical call with a recruiter lasts 15-30 minutes, so it's not something you should be doing with everyone who asks.
You'll also get a lot of emails giving you details of job opportunities that are similar to what you want, but not quite right because the location is 50 miles away or the technology is something you have no experience with. Instead of taking the huff that the recruiter obviously hasn't read your CV before contacting you, I found some success with simply responding back politely to each of these with "Unfortunately this opportunity doesn't really fit me because [reason], but if you should happen to come across any similar opportunities for [technology] in [location], please keep me in mind". A few of them immediately responded with "Oh, actually, I've got such an opportunity right here".
There's an important lesson there: Most agencies who contact you will be low-effort spammers (by virtue of statistics - they're the ones sending all the emails), but that doesn't mean they can't be of value to you.
So why deal with agencies in the first place, why not just go directly to the companies? The answer to this is that a lot of candidates are placed quite aggressively as and when they come onto the market. Some companies aren't specifically looking to fill a vacancy, but are happy to extend offers if they come into contact with a candidate who they see as a fit. Agencies are quite aggressive about getting you in front of these companies; they have both the time and motivation to do so, and the market knowledge to know which companies are receptive to this approach. By waiting for jobs to be advertised directly, you've already missed out on a lot of vacancies that never became official because someone was hired before the company considered itself to need to advertise.
You could try the speculative approach yourself, but unless you have a lot of free time to devote to market research, it's probably best to leave it to the agencies. They do, after all, get paid for it.
But some companies specifically don't use recruitment agencies... True. Some do, some don't. Some claim not to, but do. Realistically though, getting your foot into the door yourself is a bigger expenditure of effort than using an agency. If you want to send your CV to a company yourself, you need a covering letter introducing and explaining yourself. If you go via an agency, the agency handles the formalities for you. Companies who don't use agencies at all are, inadvertently or not, selecting from a pool of candidates who disproportionately are not already employed, because they're the ones that have time to jump through hoops for a potential employer. That's how it was at Blueberry Consultants, and many of the employees there were not working at the time they were hired, which is actually quite unusual due to very low average unemployment in the technology industry.
This is a good time re-state the main piece of advice here: Focus your energy on things most likely to lead to positive results (and employers who respect your time). Opportunity cost is a real thing.
But the important flip-side to all this is that when an agency contacts you and says they have a great opportunity available, it doesn't mean there's an actual vacancy. They might be just trying to put you in front of one of their clients who they've had success with in the past, but that client might not be actually open to hiring right now.
This is quite frustrating, because it means you often speak to a recruiter who promises you that you're a great fit and they'll pass your CV on, but you never hear anything more. In my experience, at the very least, the recruiter will over-egg how enthusiastic the client is; they'll say the client is looking to interview "THIS WEEK", and then it takes two weeks to arrange an interview because "the hiring manager was on holiday". It's quite normal for things to go quiet after the initial contact stage, only for the recruiter to pop up a couple of weeks later with an offer of an interview.
The reality is that recruitment agencies are in the sales business, and you've got to take everything they say with a pinch of salt. It's important to play the game, but agencies are not your friend, and as soon as you've put the phone down with one recruiter, no matter how enthusiastic they are and how much they really really think you'll get offered the job no problem, you should forget about them and start sifting through the new opportunities coming into your inbox.
My approach during my job search was to allocate the time to speak on the phone to one recruiter per day. Within two weeks, I had an offer, and the following week I had six or seven offers of interviews (which I declined, as I'd already accepted the offer). But most of that two weeks was radio silence from recruiters who had been extremely confident and optimistic of an almost immediate turnaround when I'd initially spoken to them.