The slice of life genre is fairly popular in Japan. These kinds of stories use the lack of a plot and lack of conflict to serve as peaceful escapism. This is what makes them enjoyable.
Life, observed and examined. A cast of characters go about their daily lives, making observations and being themselves. School is perhaps the most common setting for these kinds of series, especially in animation. Coming of age is often a major part of their stories.
A related, perhaps more extreme concept is iyashikei (Japanese for "healing"), which refers to anime and manga that are purposefully intended to have a healing or soothing effect.
Works of this kind often involve alternative realities with little to no conflict, emphasizing nature and the little delights in life.
Even though many iyashikei creations seem to have a strong escapist basis, the goal is not only to offer a means of getting away from daily worries, but to let the audience embrace a calming state of mind. As these works tend to involve normal people in normal situations, this trope often overlaps with Slice of Life.
If you don't mind getting trapped in TV Tropes, the above links have many examples of such works. Some examples include ARIA and Sketchbook Full Color's.
These stories don't really have much plot to speak of. The healing or soothing effect is the main draw for series like these. So, to write stories like these, the focus needs to be on the scenery and on the little things. One idea: Think back to how you entertained youself when you were really young (like 4), when everything was still new and exciting. Ordinary things like that typically fit well with slice of life and iyashikei.
See also this essay, which discusses iyashikei in more detail. Some highlights:
- Iyashikei series move at a slow, calming pace, and forgo both narrative and comedic tension.
- Iyashikei uses and creates atmosphere through heavy focus on setting.
- Mono no aware is another common theme in iyashikei. It is usually described as "a somewhat bittersweet appreciation of the beauty found in life, with the knowledge that everything in it is ephemeral".
- Iyashikei stories do have narrative, but iyashikei de-emphasizes these compared to other genres.
Plot doesn't need to be something grand like good vs. evil or man vs. nature or anything like that. Take Yotsuba&! chapters 81-82, for instance. In these chapters Yotsuba and the gang go camping. There are a lot of trees. It is fun.
What drives the plot? Well, what drives you? Why would you want to go on vacation? Why would you want to go to the swimming pool? Why would you want to go for a walk in the park? Why would you want to hang out with friends? It's the same idea.
Of course, "interesting" is subjective, and this kind of story won't appeal to everyone. Some people have fallen asleep trying to watch anime of this genre, and some people aren't really interested in reading a story about stuff they already deal with in real life, and that's fine.
As for what marks the end... Well, these types of stories tend to be fairly open-ended, so there usually isn't a clear ending point. Anywhere is fine, really. With stories set in school though, the story typically ends right around when the characters graduate. You could also end it after a significant character growth, like with Sora in Sketchbook, when she talks more (spoilers). With Calvin and Hobbes, Bill Watterson ended it just because his interests had shifted. With Peanuts, Charles Schulz ended it because of declining health (and incidentally, he died one day before his last comic strip appeared in newspapers).
So I suppose you can stop the story at a natural transition point such as graduation or coming of age, when you are no longer interested in the story, or when you are dead.