If you kicked butt, you’ll get an offer. That means there’s a pretty good chance you’ll get to work there, but just remember that not all “offers” (especially verbal-only ones) are actually real. It’s a good time to be happy because you did well but don’t expect that it’s a done deal. I’ve seen companies pull offers for internal reasons or external reasons – the point is that it happens, so don’t go buying a house until you’ve signed the documents. If it’s just a verbal offer, ask them to email you the details.
DO NOT ACCEPT RIGHT AWAY! This is doubly true if you don’t think it’s a good offer. This is an important point for you – they’ve been totally in control of the process until now and they’ve probably dragged their feet because they can (who knows, an even better developer might show up, right?). Now it’s your turn. They’ve put in a lot of effort so far and any reasonable company isn’t going to let you walk away over a few days or a few thousand dollars. They should give you at least a week to decide.
One big factor is compensation. The person making the offer usually has discretion to bump it up a bit (maybe $5k in Silicon Valley, probably less elsewhere) without asking their manager, so it’s often a good idea to negotiate the first offer. Maybe you’re negotiating salary, vacation, relocation bonuses, or personal project status. It doesn’t matter, your position is a whole lot better while you’re holding that offer.
What’s the best thing you can do? GET ANOTHER OFFER! There’s nothing nearly as good when negotiating as another offer from another company which gives you the ability to walk away. You shouldn’t be shamelessly callous and capitalistic about it (the goal isn’t to piss off everyone who gave you offers), but do take advantage of this!
Not only that, but remember all those companies that dragged their feet and you hadn’t heard back from? Send every one of them (who you are realistically interested in) an email explaining that you have an offer and need to make a decision relatively quickly. See if that doesn’t help them speed you along in the process and maybe get you that other offer. As soon as you have an offer to work with, you suddenly have all that social proof you never had before since you haven’t worked anywhere else. Use it.
Once you’ve worked through your negotiation and hopefully had the chance to rank multiple offers, the decision must be made. That’s a good choice to have to make. Congratulations! Now you get paid to keep learning.