Professional meetings count (typically), college classes, webinars, professional seminars and the like are all applicable provided they are in your field of licensure.
The state boards usually set the number of hours you must obtain to stay current. If you have more than one license, you may need additional hours.
Not all states require you to send in logs; most only require logs if you get audited. Some states don't require CEU's until your second renewal period.
Each state can be slightly different, be sure to check the rules and regulations for your state or any state you have a license in.
Once you've figured out what your board requires, get a log started and keep it updated. When you get back from a meeting / seminar, log it.