|This police officer knows what he's doing. Notice the handcuffs.|
LEGO is a brand name, and therefore should not be pluralized to describe its products. Proper form is to use "LEGO" as an adjective, with a noun behind it. For example, instead of "Legos", one should say either Lego bricks, pieces, parts, or elements (the latter being the most formal). "Blocks" is also regarded to be incorrect. To describe an entire product, say "Lego set". Kit is incorrect. Also, use minifigures (or minifigs, for short), instead of "people". If my word is not good enough, I have found some official statements from the company. The first was originally issued in 1980, and is still upheld. The second is an excerpt from the Lego company's trademark infringement rules.
“The word LEGO is a brand name, and is very special to all of us in the LEGO Group Companies. We would sincerely like your help in keeping it special. Please always refer to our products as “LEGO bricks or toys” and not “LEGOS.” By doing so, you will be helping to protect and preserve a brand of which we are very proud, and that stands for quality the world over. Thank you!”
Proper Use of the LEGO Trademark
"If the LEGO trademark is used at all, it should always be used as an adjective, not as a noun. For example, say "MODELS BUILT OF LEGO BRICKS". Never say "MODELS BUILT OF LEGOs".
First off, I will make the note that official form for multiple building elements is "LEGO® brand building bricks," but honestly that's ridiculous and nobody really takes the time to say that every time. Most often, builders will use just LEGO, though it is generally also accepted to capitalize only the "L" in an informal setting. I do it that way because if you put LEGO in all caps too many times in an entry, I find it distracting.
According to official rules, it is also incorrect to refer to The LEGO Group as simply "Lego" (It's officially TLG), and also to refer to "your Lego collection". These two rules can usually be safely disregarded during casual use, because there isn't an easier but still respectful form. The former should probably be observed if you own any different products similar to Lego, but if you despise and eradicate these knock-offs like I and many fans do, you're fine. It is also usually acceptable to address Lego bricks as simply "Lego" in a casual setting, but NOT "Legos".
These guidelines are nothing new, the first statement having been issued thirty-three years ago. It may also be helpful for you to notice that no official statement from the company has ever used the term "Legos", and some word processors even treat "Legos" as a typo, while accepting the proper form. So, out of respect for the company and for the sanity of nerds everywhere, kindly try to use proper terminology. Happy building!