Cabinet and furniture makers buy their lumber in the rough. The rough boards may be twisted or warped due to drying in the kiln as well as their individual properties. In converting the rough lumber to a finished board we follow a well established process. The process ensures the resulting board will be flat and straight when finished. When you buy surfaced lumber at any lumber yard or supplier, the boards have not been flattened or straightened, they have been fed into a foursider machine. We also want kiln dried lumber to 7-8% moisture content, MC. The boards you find at big boxes and lumber yards are often 20% MC. Not suitable for interior work. People like to suggest buying quarter sawn lumber for the inherent stability. Other than white oak, there is hardly any quarter sawn lumber available anywhere. Sounds good to say but good luck finding any.
The first part of the process is "stock selection". This can be one of the more difficult parts since it takes a fair amount of experience to be able to see a boards characteristics in the rough.
Step 2 is making rough cuts, cutting the rough boards into more manageable pieces, if possible. No sense milling a 16' board when it will be cut up into 4' pieces for the project. It also doesn't make sense to cut things too short. Anything less than 30" long will cause other issues as you go through the milling process. Normally, at least 2 extra inches are left on a rough cut.
Step 3 is flattening one face on the jointer. You don't have to surface the face completely and don't want to. Just get the face surfaced so that 80% or so is flat and can serve as a reference to the planer bed.
Step 4 is planing to thickness. The flat face gave you the reference from which all other faces/edges will be referenced. When planing, it's important to flip the boards so you take equal amounts off both faces. Too much off one face will cause the board to warp.
Step 5 is straightening an edge. It's important to cut with the grain on all the steps. If someone tries to straighten an edge after only surfacing one face on the jointer, they only have one face to register against the jointer fence. That may not allow cutting with the grain and is the reason both faces are surfaced first. Cutting with the grain will give the best results as far as chipping, tearing, splintering and the overall quality of the surfaces. When done correctly, no secondary operations, such as power sanding, scraping or hand planing are needed.
Step 5 is ripping the board to width, using the straight edge against the table saw fence. Depending, this cut edge may be run with one single pass on the jointer to remove the saw marks. This has to be planned ahead.
Step 6 and 7 are squaring one end then cutting to length. You cannot cut a square end on a board if you don't have a straight edge to reference to.
All the various woodworking joints and details you want to cut are a piece of cake once you have properly prepared stock. Many do not have jointers or planers. If you do have them, they need to be set up and operated correctly or you won't get the desired results. Without them, you are limited in your control of the stock and everything related to the project. It's
one of the reasons so many on forums have trouble with accuracy and need secondary operations to make things fit.