Don't let fancy demonstrations take away your ability to critically judge a product

Try assembling and disassembling the attachments before you buy. Think about what you really need and aim for that.)

If possible (and especially if you suffer from asthma), test air-tightness for yourself. They'll need to be sturdy, especially if you'll be using your foot to operate them.

For carpets, make sure the vacuum has enough suction power, especially with deep pile styles. For example, PVD Plating Machine many units will need a filter, after-filter, bag and maybe even belt replacements within a year's time or less. Don't be dazzled by an array of attachments.

Make an inventory of all the parts that will require replacement, how often the replacement should occur and how much it will cost you annually.

Make sure that the power switch, height level controller and any other controls are easy to access and use.

Generally speaking, if keeping dust out of the air is one of your goals, choose a bag model. Of course, they also make the unit heavier. Don't let fancy demonstrations take away your ability to critically judge a product. In general, metal components are better than plastic ones. If you have a shop vac, use it for powders instead. The best floor sweeper in the world won't do as good a job as a so-so vacuum cleaner, and an upright vacuum will handle differently than a canister unit.

Check the height of the fully assembled attachments to make sure that you won't be stooping or holding your arm up in the air to use them. Clean filters often. One way is to vacuum for a bit with a floor model and then see how much dust has collected on the outside of the unit. HEPA vacs are especially sensitive to fine powder, and vacuuming up a lot of it can destroy your investment. Make sure that they're easy to assemble, that they stay together and are airtight during use, and that you can still disassemble them with a minimum of effort.

If you or other persons in your household have long hair, get a vacuum that has a stainless steel brush roller with ball bearings.

However, bagless technology is improving, and in some higher-end brands (like Dyson), bagless models will work just as well. Vacuums that allow you to wash and reuse filters can save money, but be sure to carefully follow instructions when doing so. On the other hand, there's no need for an energy hog if the situation just doesn't call for it