Checkpoints... my sense of scale for obstacles to put in my character's way is haphazard at best. I mean just look at Rhork and Verin . They get tossed around like ragdolls
Legion answered the question quite well, but I'll add a bit in here around scale, as a device I use might help you visualize the size a bit better.
Now, for the Sanctum, I mostly free-write. I have a goal in mind of where the non-collaborative tale 'might' end, but for the most part, I sit down, step into the scene and write what comes to mind. Read it a couple of times out loud for major errors, then post. Sometimes it works, sometimes it doesn't, but my goals are accomplished all the same.
But for projects not intended for the Sanctum, I like to visualize scale, pace & intensity like a WAVE PATTERN. You have a baseline that is 0, normal, calm, self, etc, and it expands, builds from there.
SCALE: Let's say you want to start your story with a grand, expansive description of the world effecting your character. Therefore, your starting spot on the wave would be a high positive, say a 7. Then, as you zoom in on your character, it moves toward the baseline (self). Then, as you add details to the story it grows again (such as friends, associates, enemies). As it effects your character, it drops toward the baseline.
It sets up the scale of expansion and contraction, as well as rhythm (how often you expand/contract and when). You can set the scale with gradients of scope. Say 1 is the character's family. 2 - friends. 3- city, 4- town, 5- district, 6-kingdom, etc. It has to be based upon your tale, really, and where you want to expand it TO.
PACE: you can do the exact same thing, both in frequency and intensity. Let's say that the first encounter (Obstacle) is mild, so it blips to 3. The next one is 5, maybe the final one is 9. This gives you clues into how to write it. Also, how fast do you want the action coming at you? You can set the frequency, thus giving you clues into how often action occurs in the story. Is it non-stop, in your face action? Then the waves are close together.
If you want a slower pace, one mixed with big lulls, then it can have rolling waves. Or they could spike, depending upon who you like to write action. A rolling wave builds over a period of time, while the spike shoots toward a sudden, explosive bit of action, then falls off just as sharp.
While it sounds technical, it's really a simple way to "see" your story (if you are a visual person) and keep it under control from a distance. Does the story expand too often? Dial it back and change the frequency. Is the action too intense early in the story and leave you no room for a climactic ending? Dial it down.
Using your words of obstacle's, how often do you throw them at your characters? Is it constant, or do you give them time to gather their wits? How intense is each one? Are they building, or are they all at the same level of intensity? Using the ideology of a wave can help you corral the haphazard into the structured, thus creating a pleasing flow to your stories.
That's my sound and fury, Tirien. Hope it makes sense, though it signifies nothing, really.