What should I add before or after his name to show respect? In India we do that adding sir after the name but I don't think it's done in standard English.
If you want to be formal about it, Mr. Gates should do fine. Over the years I've seen a few newspaper style guides (commercial confidentiality prevents me from naming names) which adopt the following principle in referring to people in their articles:
- If the person is before the courts and accused or convicted of a crime, use their surname only;
- Otherwise prefix it with their honorific (Dr, Mr, Mrs, etc.).
I'd check to see whether it's in the AP Stylebook but I dumped many of my physical books when I last moved and that particular book doesn't seem to be available in digital format so I haven't replaced it.
Of course in the days of the 24 hour news cycle and the less than clear distinction between op/ed and journalism, the principle seems to be honoured as much in the breach as in the observance. I notice it in a number of page 1 and 2 articles, but get to the business pages and most people seem to be referred to by surname only. Get to the travel and leisure sections and first names tend to be used instead. As mplungjan said, though, I really doubt that he'd take offence at Bill. He almost has a brand on that name in the same way as Madonna has on hers.