Let me know if I can help.
Of course, this is not really establishing a relationship in which one is going to help the other. It is more of a mantra we repeat to be nice, or because we are in a position in which we are expected to help yet we have absolutely no idea how to do that (nor we want to bother figuring that out by ourselves).
In fact, it is not surprising that when an actual request follows, the person originally offering help often fails to give just that. Not because they are mean, simply because they did not intend to help in the first place. Perhaps they are busy, incompetent, unfit, disorganized, sick, committed (to something or someone else).
Let me know if I can help and the subsequent failure to help on a concrete request are two of the major failures of managers in organisations nowadays.
They are perfect, because they work wonders both in case you are one of those managers who believe it is not your job to serve – I am the boss, I can’t bother, and in case you are one of those modern managers that are all for freedom and flatness – I am very hands off, I am giving your freedom.
Next time try: Here is what I am going to do.
Figuring out what’s to be done is a job for you to complete before showing up in the conversation.