Use an editor that helps balance parentheses and automatically indents Lisp code. If the indentation is consistent with the parentheses (very easy to maintain with a decent editor) then you can mostly ignore the parentheses and just look at the indentation.
Break big functions with deep nesting into smaller functions. (Like in any language). If you have to page up and down several screenfuls to check whether multiple blocks are at the same indentation level and under the same parent, maybe the function is too big.
Break big functions with deep nesting into smaller functions. (Like in any language). If you have to page up and down several screenfuls to check whether multiple blocks are at the same indentation level and under the same parent, maybe the function is too big.