No "standard" guidelines, no, but here are a few things that I stick to.  There will be exceptions to nearly all of them!

(1) Choose the clustered index key carefully - but do include one
(2) The table should have a primary key constraint
(3) Referential integrity should be enforced with foreign key constraints
(4) Use a consistent convention for naming columns, tables, constraints and so on
(5) Don't use spaces, hyphens or a host of other characters in object and column names.  Avoid reserved keywords also
(6) Choose data types appropriately
(7) Make full use of CHECK and DEFAULT constraints.

I could go on - but I'll leave it to others to add to (or disagree with parts of) the list.

John