I made a queen but I started with some plans from Ana White and changed things as I saw fit, either because I had tools that allowed me to use better methods or I wanted a different look...

Here's a crappy picture, it weighs like 300 pounds

I'd recommend learning SketchUp or TinkerCad or something similar to make your own plans because part of the beauty of making your own furniture is it can be exactly the way you want it to be. However, that kind of software can be intimidating if you've never had exposure to it.

So, the next best thing I would recommend would be to find a video on YouTube of someone building a bed, these makers sometimes have links to the plans they used to build it. There are a lot of bed builds on YouTube and they might even give you some ideas you'd like to incorporate into your own design.

I have yet to build anything from plans I haven't drawn myself.

I tend to look at a lot of pictures for inspiration, and I'll admit to just...watching episodes of the New Yankee Workshop and just ripping off what Norm did; my parents have a very nicely plagiarized set of bookcases flanking their front door. But I often take a design element from here, another from there, and combine them into what I want.

I do tend to use the drafting process almost as a dress rehearsal for building the piece, creating the parts in 3D CAD and then assembling them teaches you things about the build.

I personally use FreeCAD, because basically nothing else is viable.

I would recommend making the plans yourself so it can be exactly what you want. You can learn CAD like some others have mentioned, but pencil and paper is just as good for keeping track of dimensions.

If your feeling adventurous and are careful enough, a bed is something you could probably build entirely without plans. They aren't much more than a glorified box with two big ends and some little legs underneath. And, unless you make it out of tissue paper and twigs, your not likely to run into major structural concerns.

I draw them up. What plans do you need for such a simple thing. So long as you have rudimentary understanding of construction, wood and grade 3 physics, you’ll do ok.