I'd hesitate to pin it down to any particular feature set, but the following two features have been very useful to me:
Date-based alarm scheduling - I don't want a feature-heavy calendar application running on my phone, so this has been useful.
Custom text for alarms - Useful for gym reminders; I can plan exercises for each day in advance, rather than deciding what to do in advance. (Again, I stay away from feature-heavy applications. I like lightweight.)
Day-based alarms, and multiple alarms, while trivial features on most smartphone alarm apps, are in fact quite useful, and weren't present in my pre-smartphone phones. I have two alarms set for waking up, for example; the first tells me to down an energy drink (Xenadrine drink mix, supposedly for dieting but my favorite energy drink, or Redline energy drinks, are both awesome for this) or extra-large cup of coffee. Thirty minutes later, when the second alarm wakes me up, I wake up easily and without grogginess. (Alternatively, you can use an alarm application that wakes you up in the ideal part of your sleep cycle. That's a bit... feature-rich for me, however.)
How do you have a cup of coffee ready to go before you wake up? I'd think it would be cold and unpleasant...
This is an extension of a comment I made that I can't find and also a request for examples. It seems plausible that, when giving advice, many people optimize for deepness or punchiness of the advice rather than for actual practical value. There may be good reasons to do this - e.g. advice that sounds deep or punchy might be more likely to be listened to - but as a corollary, there could be valuable advice that people generally don't give because it doesn't sound deep or punchy. Let's call this boring advice.
An example that's been discussed on LW several times is "make checklists." Checklists are great. We should totally make checklists. But "make checklists" is not a deep or punchy thing to say. Other examples include "google things" and "exercise."
I would like people to use this thread to post other examples of boring advice. If you can, provide evidence and/or a plausible argument that your boring advice actually is useful, but I would prefer that you err on the side of boring but not necessarily useful in the name of more thoroughly searching a plausibly under-searched part of advicespace.
Upvotes on advice posted in this thread should be based on your estimate of the usefulness of the advice; in particular, please do not vote up advice just because it sounds deep or punchy.