I think wildness offers a good overall guide on what to link or not link. As someone who writes a mix of different kinds of Hubs, I find that when it comes to what links to add or not, I like to first assess what it is I think any reader may be expecting, or may like (or at least not find "off") when he gets to the Hub. I try to be careful to treat everything I do with any one, individual, Hub on very much a case-by-case basis. I don't doubt that I don't get it right; but I generally aim to always err on the side of caution and not add "borderline-purpose" links. A borderline-purpose link to, say, an authoritative site is less borderline, though, than a borderline-purpose link to someone I've written (or even that someone else who doesn't write from an authority-perspective has written). The kind of writing I do on here isn't usually writing aimed at the "authority approach" (at all) but I don't want to emphasize on one Hub some other Hub I've written that "waters down" or "weakens" the reader's impression of my aims as they apply to the subject of the Hub he's reading.
It's pretty rare for me to link to my own stuff in my own stuff on here. I figure, the profile is about about me. Most of the Hubs are not (even if I'm "in them" by virtue of including personal experience).
If people go to a recipe Hub (not that I write those) they're there for the recipe. If they go to a "how to get a wine stain out of a tablecloth" Hub they only want to know about getting out the stain or how I did it - not that back-story about how I was writing another story and spilled wine while I was doing that. If someone comes to a "coping with losing your parents" Hub, then maybe they'd be interested in another "losing your parents" Hub. If the "coping with..." Hub was written from personal experience I may link another Hub (my own or someone else's) about something like "dealing with serious loss in general" or something that's written from a different angle than from the personal-experience angle.
Other than that; for the most part, I keep links in my Hubs to either authoritative information (that offers more, and more expert, info on whatever I wrote about - even if I wrote from a personal-experience angle) or else to any Amazon ads that I think may be of use to the reader of that Hub. (With a lot of the stuff I write Amazon ads are often confined to books about the subject.)
There are ways to design our own profile that lets us say, "I write about x (and here's a link to that)" and I write about "z" (and here's a link to that). The way I've always seen it, if a reader likes one Hub and wants to read more that I've written he'll go looking for what else I show on the profile.
Even though my own approach is a matter of my personal preference, the more important thing is that Google doesn't want articles/Hubs that aren't about the reader getting something that's "about the reader and what what's good for the reader, rather than being about me and my writing". I figure, what I may lose in terms of the slim possibility any reader would even click on a link (to something else I wrote and he didn't care about) may be made up for in an overall better impression of me and maybe the reader's deciding to go looking for what else I've written. More importantly, not having "iffy" or "borderline" or "unacceptable" links in the "eyes" of Google means less risk of being "dumped" Google-traffic-wise.
The one thing I've done a time or two, and involving the rare Hub that I've written for "entertainment-value" (to the reader) only; is that if I think the reader got to the Hub by looking for a story (rather than info, discussion, analysis, or even personal experience with one subject or another, etc.) then I may add a link to one other similar piece of creative writing. On the rare time when I've done that it's been from the "if you like this story, maybe you'll like another one" kind of thinking.
Right way or wrong way (sometimes none of us are completely sure), I think if I wrote a Hub about a recipe for a cake I'd keep anything other than recipe or something like where it came from, or why it's better than another recipe) out of it. On the other hand, if I wrote a personal experience about how I made things easy for myself when I had my child's birthday party, I might throw the recipe that made making the cake (or something else) particularly easy. In that case, though, the main purpose of the Hub would be "potentially useful personal-experience with birthday parties Hub". If the Hub was a creative-writing piece (entertainment-for-the-reader) only, I'd probably leave out the cake recipe because the reader would be there (presumably) looking for reading/entertainment - not cake recipes. (Although I think the cake-recipe example in this case isn't as inappropriate a use of linking as some types of inappropriate linking are.)
