Just a suggestion if you are still in the process: I typically use graph paper or a specialized spreadsheet I developed where each block is so much distance. I map out all of the hardscape, sprinklers, and current plants on the map and then us a different colored pencil/line to map out what I want to do next. When calculating how many shrubs to add, it's mathematics. If I want them to grow together as a screen, I take their width at maturity and subtract ~1ft. Then I plot them on a map that way and it gives me a good idea where they should be planted. If I want them spaced, I use their mature width and add X amount of feet, depending on the desired spacing. Start with your largest plants first and work down to your ground covers, smaller plants, and annuals (if you plant them).

"Is there a website you suggest that offers tips in this area?" You are there now! I commend you on wanting to draw a plan. Every person who is going to do landscape installation/construction work, should have a plan to work from before the work begins. It can save a lot of grief. It is one thing to get ideas. People are getting them here every day, usually from a perspective view and sometimes just verbally. Getting the ideas is one of the first steps, but they need to be translated into plan form in order to know that things fit, look compatible with the space and in order to make quantity calculations. (The plan will be to a specific scale in order to accurately measure directly from it,)

When you're ready to get help with ideas, start a new thread for that specific area of the yard. (Trying to do the whole yard at once is difficult and confusing.) Upload a photo spread that shows the complete area from end to end. Have the camera be in line with the center of the scene. (That is 99% of the time going to alight with the front door or center of house.) Take a full 180* of slightly overlapping pictures, starting at the far left and panning the camera to the far right. If you move the camera location while capturing the scene, it will no longer work as a scene. The camera must just pivot while you stay in one spot. Also, don't be too far away from the house or we won't see enough detail. You should be far enough away to capture the roof but not a lot of sky. And we should see about 20-30' of lawn area in front of the house, but not a lot more, or a lot of street. (That's a different picture.) At the first and last photo of the panoramic spread, we'll see the fronts of your flanking neighbors' houses. After you take those pictures, move across the street and take a single picture that shows your whole front yard at once.

Also, you'll want to start working on a BASE PLAN ... a simple plan that shows your site with house footprint, drive, walks, fences, property line, existing tree trunks (don't draw in canopy) and any important features that will remain. Don't add any extra detail such as small plants, shading hatching, color, etc. If bed lines are subject to change, don't draw them in. Only things that are guaranteed to be in the finished plan, at ground level, should be in the base plan. If there's a question about it, it's easier to add to it later, than it is to do a bunch of erasing. Keeping it simple will make it easier to understand. (I've seen many landscape plans so complex, that they are difficult and time consuming to read.)