That is what I do, I have a 4 character personal salt, like "7Pd$", and put it in the middle of a lowercase word or phrase. Having a symbol, lowercase letter, uppercase number, and number will satisfy most password requirements. I use it on many sites, so it is easy to remember. It also makes it simple to write passwords down, e.g. "correct horse ^ battery staple" which means to me "correct horse 7Pd$ battery staple", but would not be useful to someone who saw it, since they don't know my personal salt. A combination of what xkcd said and a short personal salt that's easy to remember is probably best.

You might want to read the cartoon again to see why this is useless, counterproductive advice.

Yes, but the salt could also be useful for sites that require passwords to include a number, a non alphanumeric character, etc.

If this kind of thing takes off, it will become easier for dictionary based password attacks. Using this advice would go a long way towards preventing this.

Easier, yes, but not easy. A dictionary attack on 4 words is the same as brute forcing 4 letters except now instead of just 26 letters there are thousands. 2000^4 vs 26^4 = 35,000,000% more to check.