I generally write some naïve code and if it doesn't work, get out the debugger and fix it from there. I can work a lot faster when everything is laid out and I don't have to guess about what the data structures are going to look like. If it's performance sensitive like some tests I've seen, I'd use a profiler. I often use the jetbrains find and replace tool, as well as the search tool, I also like that I can click into the source code for libraries that I use, so I don't have to guess about the interface or implementation. Stuff like coderpad takes away a good portion of my tools that I would use day to day, I taught myself to code in notepad, but I purchased the full suite of jetbrains tools years ago so I wouldn't have to fumble around with inferior tools.
A profiler will tell you whether a O(n log n) algorithm with a very high constant factor is better or worse for your situation than an O(n²) algorithm with a very low constant.
