When I was a young writer I had a novel accepted by the Bodley Head Press in London. Unfortunately the first editor working on it became pregnant. It was passed on to a second editor who also became pregnant. I like to think it must have been a very exciting novel. Unfortunately however the Bodley Head were no longer able to publish the novel. By way of compensation they got me probably the best UK children's fiction agent at that time, Gina Pollinger (who I'd met at a BH launch party). If I'd sent her my shopping list she'd have sold it for a four figure advance. Sadly she retired a few years later and sold the agency. I then learnt that not all agents are equally proficient! For most of my career since I have represented myself, but now that it's so hard to get publishers to read your work, I've tried to get an agent again. Despite 60 titles, some very successful, I have been rejected by every one I've approached, and I have to say some replies have been fantastically condescending, with some thinly disguised ageism for good measure. I have to say I am still getting books published and now have the extra motivation of wanting to prove them all wrong!
Sanderson has a LOT of material about which is designed to help aspiring authors. Aside from the Writing Excuses podcast, he has a few entire lecture series on Youtube. He teaches a writing class at BYU, and every couple of years he'll get someone to record it, and stick it up on Youtube. They cover similar ground each year, but they change up the format and guest speakers and so on, so you get different information each time. Here Here And here are a couple of the playlist links for his lectures series.