How to focus on effectively applying for jobs with reputable employers?

I've been having a lot of trouble getting a full time job. To fix this, I want to move away from sending out massive amounts of resumes and applications through sites like Indeed and LinkedIn (I think there's a lot of fake jobs on these sites). But I'm not sure how to go about doing a more target approach. For example I've gotten the names of a couple of large, stable employers in my area that I've heard good things about. So should I just keep watch of their job posting and apply if it's a good match? Should I try to figure out specific information, such as their tech stack, so I can practice it before a job opening comes up? I've heard of trying to get "informational interviews" with a company you may want to work at that doesn't currently have job postings. How exactly is this supposed to work, it's not likely a manager is going to meet with a stranger for coffee just to share a bunch of details about the work place?

TL;DR If you already know which company you want to work for, and they have an office in your area, how would this change your job search/application approach compared to just applying to random companies?

Update: I'm not sure it makes a difference, but a lot of larger, reputable employers in my area use third party recruiting firms for hiring new employees. Often times new employees start on a fixed term contracts.

So should I just keep watch of their job posting and apply if it's a good match?

Yes

Should I try to figure out specific information, such as their tech stack, so I can practice it before a job opening comes up?

Yes, but no need to over rotate on this. Either you have the tech skills, or you don't: cramming for a few days won't make much of difference. Related skills are often good enough

... "informational interviews" ... How exactly is this supposed to work?

That happens rarely and is typically constrained to job fairs, industry events, etc. or other larger gatherings where are a lot of relevant people are on one spot. I have never seen "informational interviews" in-house.

If you already know which company you want to work for, and they have an office in your area, how would this change your job search/application approach compared to just applying to random companies?

1. Monitor their websites(s) for job posting
2. Gather as much about publicly available information the company as you can
3. Try to network: attend relevant professional society meetings, related clubs or meet-ups, and just keep your eyes and ears open for people that work there and could help you make contact. Keep it professional, don't stalk.
4. Once you have a solid body of research you can pro-actively reach out to the recruiting department with a message that clearly shows that you have done your homework. You need to impress the recruiters with the quality of your application and underlying research.

IMO quality beats quantity anytime. If you see a promising opening (local or not), take the time to research the company and write a thoughtful and customized cover letter that shows that you care. High volume scatter shot applications don't help anyone.