What factors should you take into account? I like a short snappy title. My current Novel / Novella's title is to be just two words. The cover troubles me a little more. Although I don't expect to be published, I would like to create an artwork for the front of the book if I ever do get it printed. I was thinking simplicity and subtlety. How would you choose?
If you go with a traditional publisher, I don't think you have any say in the cover. If you're going with self publishing - you should think about sizing your artworks pixel count ( certain sites will give you good advice but if you're going through Createspace or Smashwords they want exacts.) You need clear pictures that give readers a good idea of what the story is going to be about. Also, something that sparks interest. If you're doing genre check out the competition ( especially the top best sellers. Look for trends. ) Certain fonts are shunned so make sure you pick a good quality, easy to read font. Don't make it too busy or employ a lot of special effects. You want your reader to get a vibe from your design an impression, you don't want to create confusion. I've been trying my hand at self publishing. I scoured the internet for free Victorian artwork found something I liked and made up my own cover. I've also been working on several more. I totally love vintage & retro so it's a huge influence on my designs ( might not help me sell but who knows. ) I usually pick short titles but occasionally a few have come out long - here's a link to some of my battles with cover artwork - https://www.writingforums.org/threads/fiddling-with-covers-for-e-story.131495/page-3
If you are using artwork taken from the internet, make sure it's not copyrighted to someone else. Failing that, grab your camera and go out and play. That doesn't mean though, that the cover has to be a landscape/scenic picture. Look at shapes, textures and colours. You'll be surprised what you can do with a piece of silk and a couple of lamps. On the subject of fonts, please, I beg you, stay away from Papyrus, Comic Sans, Edwardian Script, Curlz and anything that resembles handwritten text for the cover. Titles, that's completely up to you. I personally, don't like book titles that start with 'The', but that's just me.
i agree with Peachalulu's advice on covers for your novel. in terms of a title, go with what works for the novel, it sounds like a simplistic approach, but there is an art to getting a book title that works with the novel. and dont be afraid to change it several times, my second novel has gone through about four or five titles before i settled on this one... cutecat also has some very good points on covers and titles/fonts which i agree with, especially on making sure that the title can be read.
And as well as researching covers of books on the current marketplace, have a look at some 'what not to do' sites too. Google lousy book covers.