 question particles in yes/no questions tend to appear after the word they mark, and they tend to appear more in type II and III languages; when they appear in type I languages the particle appears before the word they mark. Auxiliary verbs, too, show interesting syntactic patterning that follows from the generalization about consistent head positioning.
Morphosyntactic universals are in between syntactic universals and morphological universals in that they involve morphological tendencies in relationship to syntactic features. For example, what we find is that morphological items tend to behave similar to heads in PPs, in that if a language has just suffixing, then it should behave like a language with postpositions and be type III, and indeed this turns out to be the case. Indeed, if a language has just suffixes then it has postpositions, if it has just prefixes then it has prepositions.
In the case of agreement between nouns and adjectives, N languages always have agreeing adjectives. More generally, type III languages almost always have case systems. The full complexity of syntax related tendencies among languages is beyond the scope of this section, but you can read more about them here. Some of the implications that we can derive from these universals would make a nice set of grammatical rules. For instance, the tendency for affixes to behave like adpositions might indicate some hidden structure that involves the affixes as the head of some adposition-like phrase, undergoing some sort of historical change from an adposition to an affix, thus giving us an idea of how to evolve a constructed language. The tendency for languages to try to be consistent in their head positioning could result from a historical process that changes parts of speech into one another. Alternatively, to make a truly alien feeling language, these universals could be reversed, making a Po type I language or something similar. Knowing the universals clearly makes it easier to create both a naturalist language as well as interesting alien languages.
Greenberg, Joseph. "Some Universals of Grammar." 1999. 10 Dec 2007 <http://angli02.kgw.tu-berlin.de/Korean/Artikel02/>.