It’s NHL trade deadline day, which means we can expect something like 15 or 20 trades to be announced by the end of the afternoon. Of course, not all transactions are created equal. As a quick primer, here’s a half-dozen types of trades to watch for today.

The blockbuster

A superstar is on the move, shifting the balance of power of the entire league in a single bold transaction!

How often it happens: Several times on deadline day, assuming you’ve given up on the broadcasts and started playing the GM mode on NHL 13 instead. Otherwise, never.

How you’ll know it when you see it: Air raid sirens go off, the emergency broadcast system is activated, schools and day cares are closed down (Canada) and/or somebody in your Twitter feed briefly mentions it (U.S.).

The trade that would have been a blockbuster, if it happened five years ago

Jaromir Jagr, we are looking in your direction.

How often it happens: This is a much more realistic option. Teams that should be sellers love to hold on to their assets too long, and buyers seem to love settling for name value versus actual production.

How you’ll know it when you see it: All the awesome highlights they’re showing of the traded player seem to be in standard definition.

The fire sale

Maybe we’ll get a prospect, maybe we’ll get a pick. We don’t really care. We hate this team, and want everyone out of here by Thursday.

How often it happens: Each season there are always a few teams that fall into this category. (This year, it looks like Buffalo and Calgary.)

How you’ll know it when you see it: You can’t help but notice that the GM being interviewed about the trade from his office is discreetly packing up his desk as he talks.

The trade with the prospects who turn out not to be prospects

A trade scrolls across the ticker that mentions some prospects you’re not familiar with. So you click on your favorite prospect site, find the team’s depth chart, and start scrolling … and scrolling … and scrolling …

How often it happens: Pretty much every time Jay Feaster picks up the phone these days.

How you’ll know it when you see it: You start hearing phrases like “overage” and “undersize” and “one of the better 27-year-olds in the ECHL.”

The trade that’s way more complicated than it needed to be

This is the trade that involves a decent player or two, and then for some reason a seventh-round pick and a conditional fifth and also a swap of sixth-rounders in 2017.

How often it happens: Every time two stubborn GMs get involved in a battle of wills over who gets to make the last demand.

How you’ll know it when you see it: It gives you flashbacks to every fantasy football trade negotiation you’ve had with somebody who works in a sales department.

The guy you’ve never heard of for the other guy you’ve never heard of

A deadline-day staple in recent years. For some reason, these tend to be one-for-one deals.

How often it happens: Whenever two GMs realize they’re about to get ripped in the local media for not making a single trade on deadline day.

How you’ll know it when you see it: The poor guy on the broadcast panel who has to “analyze” the deal on live television is clearly Googling frantically as he talks.