Are any kind of wood-chips good enough for smoking?
You can't just pick up any old wood chips but you can get ones for cooking at the hardware store. Even Home Depot or Lowes should have wood-for-smoking available.

You have to be careful since if you get chips made out of treated lumber for example the resulting smoke could be poisonous. Probably not something you want to eat. You also want to avoid poisonous wood or trees.

Warnings aside, you can use just about any non-poisonous hardwood to make woodchips.  Just make chunks or chips out of nice dry seasoned logs.  Usually, people use wood with interesting favors to add such as fruit tree woods (apple, pear, cherry). Other popular woods are mesquite, hickory, or maple.