Whether you are following the Skill Builder video tutorials or whom ever`s on You Tube. Two things that stand out are, why your model fails to match up. Or the struggle with positioning or selecting.
If you do a split screen, go back and forth minimizing. Or watch video from a laptop and model it on a desktop. I have had were my drawing results are out of alinement or caused issues that did not happen in the video. My not paying attention or assuming was the culprit. SU will tell you were you need to be from tool tips or the instructions~direction bar (I call it for lack of better/proper words). The area in the lower left-hand corner supplies you options or instructions. You most likely continued from the wrong end point as there are 4 posable ones to select from. Depending on if your in a opened component or group and such.
If you are not zoomed in and are paying more attention to the video, you most often dont realize the point you picked is the wrong one. Well you do, 15 minutes down the road. Also when doing a move/copy of a component and in a hast. You do not flip it on axes and then further along in assembly major issues arise.
The other is inferencing and using the cross haired courser to model with. When trying to draw a line off axes, especially arches they go their own way. This courser option carries a copy of the canvas origin axes convergence points with it were ever you move it. VERY ANNOYING at first but you quickly will get over it as it saves you many headaches. You need to select it from Window > Preference > Drawing selection.
It, with SU`s inferencing feature will allow you to find the exact point or position the first time out. With the Shift constraint option and the tape measure tool you can quickly and accurately. Map out your shape or object to be modeled. Seeing were you may need to modify it and then draw it out completely one time. It helps remove a lot of the frustrations that WE do to ourselves because of our limits and understandings. Some screen shots to to give you an idea and for you to try it out on your own. To see if it, or how much it will help you out.
Just a few simple things to make your life a little easier as you move along. As soon as I think I have figured something out. There is a new tool aspect or a feature option to take its place… so all the tips and “other approaches” to the same problem should be explored. …Peace…