Knowing the approach to solve a D challenge

[aberba]

D has tone of features and library solutions. When you encounter 
a problem, how do you approach solving it in code?

1. Do you first write it in idiomatic D style or a more general 
approach before porting to idiomatic D?

2. Do you find yourself mostly rolling out your own 
implementation first before using a library function?

3. Do the use of generics come out of first try or a rewrite?

4. What rough percentage of phobos knowledge is required for 
reasonable good problem solving efficiency?