I want to add a bit to the flow of users, by making the first form field auto focus on page load.
Initially the auto focus scares me a bit (sometimes called offensive). But as said in that Q&A, pages with the form as the single purpose of that page are a very good candidate.
I was wondering if there is some way it can be done right. For example I'm thinking of not doing it when the user already has put focus on some field itself. Are there more ways I can make sure the auto focus is not 'offensive'?
I'm looking for a bit more the whole picture. What are all the measures one should take to make this work well? Including ux, technical, visual, etc. For example, what to do when the field(s) are pre-filled by the browsers password manager?