Programs I Use or CAN Recommend
I use Word from Microsoft. Some rave about programs they use that are site-based. I won't have it. They are limiting. They don't transfer right to print or ebook or some other "why would I do that!". From a word document, I can create anything. I've gone as far as creating buy buttons in the program because it's actually that versatile. All the PDFs on my site were created using the program. All my published books, too.
Some claim only use InDesign!
Nope. Unless you know you want an epub the program is bulky and costs far more to own. For the average person, this would be a waste of time and resources. I own it just because I own the full Adobe CC program but I only use it when a children's book format will come out best by doing so, typically when someone sends me images in a two-page spread instead of individually.
Adobe Photoshop all the way.
Illustrator is hard to use and not really a reason to use it unless you are an illustrator.
InDesign, see above. Bulky and limiting compared to what I can do in photoshop
I also use photoshop to produce all the printables for tshirts, stickers, etc.
Adobe Creative Cloud Express. Site-based program with better usable features than most of the site creators. You get access to some free images but not a lot of graphics. If you want to use a site to make your cover and not a designer, I recommend this for the quality of the download and the features available.
They have a version for video too
Quick Video to show how easy this one is to use
Canva is good for social media posts and stealing graphics from. There have been recent questions on the copyright agreement and I'm watching close. Doesn't have features as good as Adobe but far more images and graphics on their free account. I have several Templates that you can purchase to use over there if you don't know where to start.
They have video too
Quick Video to show how this one works
PlaceIt has nice 3D models to drag and drop your merch into. This is a big push right now. Consumers want real people in your images. The link is set to go straight to book mockups but look around at their other services while you are there. I think this one costs for the good stuff
WHAT NOT TO USE
Any program that won't give you the ability to change the size of what you are working on.
Any program that will only allow you to work in pixels and not inches.
Any program that won't let you change the DPI you are working with or at a minimum keep it as you uploaded.
Any program that won't let you have cover images at a minimum of 1,000 x 625 pixels, and recommended at 2560 x 1600 per Amazon's requirements. I don't create anything at the minimum.
PPTX (jpg, png don't render high enough dpi)
ODT (formatting will not transfer)
TextPad (yes people have tried)
Canva (people try to ask me to change their PDF after the fact all the time. Doesn't work that way.)
Basically, anything that loses formatting when downloading into a word document for formatting.
Or won't give you the quality of covers required.