I think Russell gives some sensible advice in his short (3 pages) essay How I write. It can be found on the net and in this nice collection of Russell’s works. Here is the relevant part:
“There are some simple maxims-not perhaps quite so simple as those which my brother-in-law Logan Pearsall Smith offered me-which I think might be commanded to writers of expository prose. First: never use a long word if a short word will do. Second: if you want to make a statement with a great many qualifications, put some of the qualifications in separate sentences. Third: do not let the beginning of your sentence lead the reader to an expectation which is contradicted by the end. Take, say, such a sentence as the following, which might occur in a work on sociology: “Human beings are completely exempt from undesirable behaviour-patterns only when certain prerequisites, not satisfied except in a small percentage of actual cases, have, through some fortuitous concourse of favourable circumstances, whether congenital or environmental, chanced to combine in producing an individual in whom many factors deviate from the norm in a socially advantageous manner”. Let us see if we can translate this sentence into English. I suggest the following: “All men are scoundrels, or at any rate almost all. The men who are not must have had unusual luck, both in their birth and in their upbringing.” This is shorter and more intelligible, and says just the same thing. But I am afraid any professor who used the second sentence instead of the first would get the sack.”
I think the first two are excellent advice and I am not sure about the last one. Perhaps because I am unable to find a good example. His own (fictitious) example also differs in other important aspects, such as being contrary to both advice #1 and #2.