Tip number 1: backgrounds
A good, well-planned background is the key to an interesting interview set-up, and when you have just one person talking to the camera, it's often the thing that separates the good from the bland.
Generally speaking, avoid a blank white wall as a background, unless you have plenty of light (you may have seen the short Film 4 interviews with well-known actors where this is done well) and you can keep it from looking dull (or you have enough other stuff in-shot to keep your viewer busy).
Infinite black can work nicely, but again, it, and your subject, need to be lit properly.
Fancy doing something different? Add a painting to the wall or use a window so we can see through it into the busy streets below (particularly if it's important that you show where the video is being filmed). It isn't all about shallow depth-of-field.
Plants can be a life-saver on a shoot as well – just be careful not to make it cluttered and to watch out for clashing colours and shapes.
Tip number 2: movement and variety
Ever watched a film composed entirely of static shots? Joanna Hogg handles this simple yet challenging technique rather masterfully in her films, cleverly avoiding blandness by using intense conversation and carefully considered awkward moments.
Archipelago – starring English super-star Tom Hiddleston, the same guy in the new Jaguar adverts and that nice well-to-do bloke who's become known for being a bit of a nasty villain in films like The Avengers – is a fine, awkward-silence fuelled example of this.
That said, an entire novel could be written on why using motion in cinematography is quite a good idea. So, the point is, keep things different. By combining well managed hand-held shots with static ones, you'll create something much more varied.
Tip number 3: less about who you are, more about how you do things
Audiences have high expectations these days, obviously, so simply telling them that you provide a service by way of a 3 minute web video isn't going to cut it.
Keep your script from being bland by revealing interesting facts, reasons why people use you, and additional benefits that aren't immediately obvious to those outside the company. I'm happy to help you organise these ideas.
Last point: don't be afraid to use humour every so often. What makes us smile is what makes us re-live things and, ultimately, want to buy things – you can do absolutely no harm by entertaining people along the way with content that makes them want to come back for more.