Everyone is well aware of how Assumptions can make an ass out of you and me. Typically, then, people tend to think of assumptions as bad things, to be avoided at all costs, often while they're making an assumption about something (like assumptions).
A brick can be a bad thing when it careens into your house through a window. A brick can also be a good thing, when it makes an awesomely cheap but very useful book shelf for some poor college student who wants books off the floor. You cannot assume a brick is a good or a bad thing--its what you're doing with the brick that makes it so.
Assumptions work in the same way, but are more delicate for human beings because a) we're trained to make assumptions in order to process data, b) making an assumption typically involves dropping our primary defense--thinking about something--for a variable we're reasonably certain is equal to what we think it is (but might not be) and c) often times, because of (a), we don't always know we're making an assumption, until it hits us like a brick careening through a window.
There is a lot of social psychology work out there on the formation of assumptions. Traditionally, assumptions happen when we lack additional facts but still need to move forward. Because a decision has been made, we often don't revisit it after we've progressed further to get additional data. That is the intricate flaw in assumptions.
However, if you look at assumptions as variables in a math problem, assumptions can be filled in later--this is because for a math equation to work, you have to do the entire equation; you have to look back at the assumptions made and the variables selected, put in values, and process the thing as a whole. Likewise, with the brick, you may be building a cheap shelf, but you might not see, until half the book case is made, that one of your starting bricks was smaller than the others leading to structural integrity issues.
Speaking of integrity, assumptions and integrity go hand in hand. Its not that the most experienced people make assumptions and, because of their experience, their initial thinking is "good," it's because they go back and review their assumptions to maintain the integrity of a project/problem/personnel issue/whatever. And they do it quite a few times, every time they think of that thing.
In high school and college you sometimes got assigned to group projects. I had a nice diatribe about them an in earlier post, so you're probably wondering: what has this got to do with assumptions? Well, as a manager or a member of a group project, there comes a point when you cannot see the people you are working with. You have to assume they are doing their work. You have to let them take the time they need to put their brand on things, to get out of them their dreams and passions, or at least a really, really good spec. You have to let go, and you have to start with the assumption that people who work with you and for you will actually do their jobs.
Being a good manager, however, is finding a way to have contingencies around that so that if that person does do their job (your assumption is correct), they feel you were supportive and believed in them the entire time. However, you also need to be covered in case one of those people assumed somebody else would do the work, or that you and they wandered off with two different sets of assumptions and ended up with the wrong final product.
This typically happens with a new boss to team relationship; you don't know how you all work together, and you won't until you've had a few successes and you've had a few failures. This also applies to when you're "loaned" to another team or other teams are loaned to you--when you're working with a vendor, for example, who provides you dev resources while you manage a specific project.
So how do you make it work?
I'll talk about over communication in another entry. Sufficing to say, you cannot talk to people enough on your team. And you shouldn't be interrogating them; you should be asking them how things are going. I'll also talk about removing impediments (Yay Agile/Scrum!), in a later blog post, but that's another item that you can use--ask them if they are blocked on anything so you can help them.
Then listen to their responses.
Some people are naturally shy and will do monosyllables. Most people, however, will either at least talk a little about the work they're supposed to be doing and where they are, talk a lot about it, or divert/deflect to a different subject. Those who are monosyllabic and those who divert are those that need your additional attention--those that change your assumption from "this is getting done by these people" to "um, maybe things aren't getting done." As you re-examine that assumption, you can provide other methods of communication in case that person prefers, say, email. But after a day or so of poking around with no solid answers, the assumption can be revised to "I need to do something to make this happen."
As an aside: the verbose, confident sounding people can sometimes be the ones not getting their work done, too, but they're better at hiding it.
If you need to do something to make something happen, what do you do?
It depends on the person. You can always ask what else they're working on; if you get a 10 minute excited discussion, then that's probably why they aren't working on their project for you. If they don't know what else they should be/are working on, you can start to troubleshoot that particular individual: revisit specific guidance on priorities and come up with goals for each day, end of day, to help keep them on track. Some people make the assumption that if they are stuck, they should wait until someone comes and helps them, and this type of touching base can a) make that seem like a really bad idea and b) get them on track for what you'd prefer to be assuming: that they are doing their expected work.
Times do come when people fail to meet your expectations (which, in and of themselves are assumptions of a type), and you have to deal with one of the more unpleasant parts of managing: making corrections. Most of the time, however, you'll find that the reason that people didn't meet your assumptions is not out of laziness or malice, but out of ignorance and/or lack of communication.
Never attribute to malice what can easily be explained by ignorance.
Which leads me to another thought on assumption: one assumption you should always have is that the person with whom you are working is trying to do their best, according to his or her ability. Working with this variable in place in your equations makes it easier to stop a moment and find out what is really blocking things and how you can help them, rather than you feeling disappointed and feeling like you need to punish them. Very, very rarely are people who are being paid to work with and for you actually trying to fail you.
Keep that assumption in mind, and the rest of them are a lot easier to manage when they need to be altered to fit the formula of what must be done.