The best place to start is to study pinyin, to learn the different sounds and sound combinations in Chinese. There are lots of great websites to help complete beginners get started in Chinese. I used Chinese class 101 and Ask Benny.Btw when I say study Pinyin, I mean purely to help with sound recognition and speech, you should learn to read han zi, dont use pinyin to write with!

You could study the pinying(拼音) of chinese first. It‘s the basic thing.

You can learn a character under its radical.

The best way is to get a good course and start from the beginning of the course. Berlitz has some good ones, there are more on the market. The "Michel Thomas" method is also very useful and his courses are quite low priced. His method focuses on sentences rather then 1000's of words.

As mentioned above pinyin is to start with ,then gradually and simultaneously you learn the characters 'hanzi' and accumulate vocabulary then. You need to start with a teacher just for an overall idea ,then you can depend on online sources.