Usually, the syntax you're using will work. For example, if I enter:
I will get all questions that have "intitle" in them, including this one. The related post details how to get results that have a specific combination of words, but as long as your inquiry is only a single word, you need no special formatters. This is all you need to know about "how you get only results with a certain word in the title?" in general.
The problem with your particular inquiry is your choice of word "should". The word "should" is one of several words that are stripped out of the search. Other words would include "this", "you", and "of". If you enter them plainly, then they'll simply be stripped and leave the rest of your inquiry. In your example,
intitle:1 should becomes
intitle:1. Which gets you every question that has words in its title.
Using + or "" with these stripped words doens't really work. I don't know how it reaches this conclusion, but the search simply believes that no posts ever contain those strings. So since the search doesn't think any question contains "should", then you'll end up with blank results. If you didn't have the
intitle:1 term, then you would end up at the standard no results page.
The advanced search operations like intitle, as well as tag searches, do not bring you to the no results page if there is nothing that satisfies the criteria (like say views:231488553), and just show you an empty search results. So since no question contains "should", then
intitle:1 "should" and
intitle:1 +should both yield blank results pages.