Here is a little story about colleagueship among writers.
Recently, I went to a fantasy convention as a writer and had a slot for a reading that was one hour long. I also had a table for my books for the whole weekend. However, one of my writer colleagues just got a book table, yet not a reading slot.
Now I don't know if you have ever been to a fantasy convention, yet during such events readings are normally what brings people to get interested in someone's books (unless he or she is already a bestselling, well-known author).
So I told him I would share my slot with him, so that each of us would have 30 minutes to present our books with a reading.
He agreed and was grateful. The convention team also agreed and we made some last minute advertisement changes for the occasion. And it was a real nice reading. We even spontaneously interviewed each other a bit afterwards, because there were a few minutes left.
From what I learned by some other writer colleagues, it's best to not behave like competitors in the writing community. Because readers read more than one book. So you can recommend other writers and other books, too and everyone benefits from it. I regularly visit a regulars' table of writers in my city and it's really great how nice the other writers are. For instance, we exchange flyers and book marks, so if one us cannot go to a book fair or convention, other writers take his flyers to the event and vice versa. We even sell each other's books sometimes.