Hello. I haven't posted in a while, but so pleased this thread is still active, and hope it will still be going strong by the time I submit again in a month or so.
I'm just finishing work on the new draft of a novel I submitted back at the beginning of last year, but I sympathise with anyone waiting for news, and having to cope with rejections. It's a really tough, drawn out process, and if you're feeling particularly downhearted, I recommend reading (or re-reading) the Harriet Tyce blog that I posted further back on this thread. A reminder of what a very long journey it can be.
Brilliant advice from @kungfupannda all round.
For what it's worth, here's what I've learnt over the last few years.
In today's market, it seems your novel has to have something that makes it stand out from the submissions pile, a character, a theme, a story. Agents love great writing, of course, but they're also looking for that little glint of promise or magic.
The Mslexia Novel Competition offers general feedback taken from the overall submissions, and is very useful.
There is so much to learn about how to craft a marketable novel, a basic knowledge of the three act structure is helpful to have for a start, even if you choose not to adhere to it, just to have an awareness of your mid-point etc.
There has to be a reason for the reader/agent to keep turning the pages. Every scene or chapter must earn its keep. (And further along, pretty much every line too!)
I've posted further back about the various courses I've discovered along the way, so won't repeat it all here, but I feel I've learnt a huge amount from all of them.
Good luck to everyone. I'm grateful for this online companionship.