You can start taking your temp from whenever you like. To get into the habit, it' good to do it every day starting from whenever you're ready. So if you're thinking of TTC in a month you can start now, just to get into practice for when the time comes. You can use a regular thermometer without any problems, but a basal thermometer is more accurate as it gives a reading to two decimal places.

It's up to you how you count CD1. For me, as long as it's during the day time I count it as CD1, once it hits about 5pm I don't count it until the next day. You just have to remember to be consistent each month & count CD1 as the first day of full flow, not spotting.