I recently got a Motorola Q smart phone, and was puzzled for quite some time trying to find the underscore “_” character which some people use in email addresses.
Unfortunately, the answer is not very simple, but it does work, and also allows you access to a slew of other keys that are hard to find otherwise:
In order to insert an underscore “_” into any dialog, first press the “alt” key, the one you normally use to insert numbers. As soon as you have hit that key, hit the “shift” key, the one that allows you to enter capital letters. Once this is done, you’ll be presented with the character input screen. Funnily enough, the underscore, _ , is the first symbol listed, and you can simply tap right, then select it.