Writing is complicated! In the scrum of trying to express your inner thoughts in print, it's easy to lose sight of details like "am I one person or more than one person?" These days, I often see writers using "we" or "us" to refer to themselves, which is problematic, on account of there is only one of them and all. To prevent this all-too-understandable error, I've prepared a handy guide for when you can use "we" to refer to yourself.
1. Is more than one of you writing the sentence in question? Is it a collaborative work, authored by more than one person? Are you in some sense speaking for a group which was involved in the production of that text, or the project which that text describes?
2. Is your text a narrative or story, written in first person, in which events occurred to both the narrator and others?
3. Are you a monarch, regent, or similar figure of aristocratic leadership in a tradition where the ruler is understood to embody the state?
4. Are you an insufferable twat?
If the answer to any of the above is "yes," congratulations! You may refer to yourself with "we." If the answer is no, stick to "I." Alright, che?