Not a native, however here are a couple of observations on my part between my learning experience and the semester of 書道 I studied when I was in Japan. 大丈夫 has always been a favorite example of mine to use for this topic, because I can't think of any other word in Japanese that composed of more similar, yet different, characters. The first two (大丈), in particular, use all of the same strokes and types of strokes, just with the short leg offset to the left a bit.
Likewise, if you compare 夫 with 天, a slight change in positioning can produce a radically different character. In this case, however, you also have the lengths of the horizontal strokes to help provide an additional clue in the case of sloppy handwriting, as 夫 has the longer stroke on bottom while 天 has it on top.
Going beyond the mere positioning of similar strokes, however, using the right type of stroke can make a big difference in some cases, especially if it ends in a hook or a sweep. For an example that uses both of these, let's look at 月. If we ignored the sweep on the left vertical stroke and the hook on the right—just drawing straight lines that extended further downward—it can cause confusion as to whether it's supposed to be 月 or a sloppily-written 日 whose bottom stroke was written a bit too high.
Likewise, the types of strokes and their positioning matters for making sure that 人, 入, and 八 all remain distinct. In the case of 入 and 八, the right-hand strokes both have a flat that points off to the left prior to descending (though in some fonts this may be optional in the case of 八). In both cases, however, making sure that the strokes are connected at the top for 人 and 入 helps prevent confusion with 八, and vice versa.
These are just a few examples off the top of my head from someone who's probably spent far too much time studying kanji. If I get a chance tomorrow, I'll see about adding some pictures to illustrate the points a little bit better.