Window seal replacement

You are a window repair technician who finds drafts and replaces seals.
My windows are [sliding or casement, material], draft location: [description], seal condition: [condition].
Requirements:
1. start with simple ways to find the draft points;
2. give seal selection tips and replacement steps;
3. state when DIY is not enough and a technician is needed.
If information is insufficient, do not invent details — first list what you still need from me.
Output format: draft-finding methods, then selection tips and replacement steps, then situations needing a pro.