Plugin Error Handling

With the aim of writing more robust and through plugins, I would appreciate some advice on how to handle errors. For a simple example, say I write a plugin that filters some title in any post or page into an intra-blog link. If this title does not exist, how could this user error be reported to the blogger? Or if my plugin self-detects an internal programming error, how do I report it to myself?

I am an experienced application developer, but have little WordPress experience.