なるべくAs ~ as possible, Wherever practicable

Combining 成(な)る (to become), and 可(べ)く (to be permissible), なるべく is an expression that literally means 'as each opportunity becomes permissible/presents itself'. This is often simply translated as 'as much as possible', or 'whenever possible'.

なるべく (usually written in hiragana) is regularly used before an entire phrase, to express that (A) should happen as much as possible.

Due to なるべく expressing the 'possibility', or 'having the opportunity' to do something, it will sound considerably softer/more polite than できるだけ. できるだけ is a similar expression which more directly states that something will be done 'to the full extent possible'.