First Of All
To Start With, Firstly, To Begin With
The kanji means previous. This is an adverb version of that word. It's a little thing you can begin sentences with. You can't start your sentences with "previous" but you can start it with "First of all" or "to start with."
This is usually written without kanji though, so keep that in mind.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. In fact, the reading for this word is very rare, and kind of an exception. We'll use a mnemonic that uses both the kanji part and the hiragana attachment part.
First of all and to start with, you have to make it through this maze (まず).
First, cut the tomatoes.
First, draft beer. Then, rice.
Why don't you date a little more first, and then propose?