If you go to an interview, you can probably suss out which are stringing you along and which want to hire quickly. Ask if they need a candidate immediately or are taking their time. Ask if your qualifications are exactly what they're looking for, and if you feel like a cultural fit for them. Ask if they have the budget and headcount to hire you immediately. Ask which teams the people interviewing you are on, to find out if they are all in different teams/departments or the same. Ask if each interviewer even knows who the the previous interviewer is in the company ("Frank who?"). Ask if they know exactly what they want you to work on. Follow up periodically to see if they are responding to you in a timely manner.
It's common for there to be some uncertainty with one or two of these things, but if there's a lot of uncertainty, you are being strung along. Best case they are waiting you out trying to find a better candidate, worst case they don't even have the budget for you and are playing politics within their company using you as leverage.
Interview multiple places in parallel, and don't cancel any interviews until you've got a signed piece of paper. But of course, prioritize the ones that aren't jerking your chain.