24. Only use language you have seen or heard
My own advice to a language-learner, from the very beginning, would be extremely simple and straightforward. Never use language that you have not seen or heard and which, as far as is humanly possible, you therefore know to be correct. This is at first an extremely difficult discipline – but only, I would emphasise, at first; like anything else it will rapidly become second-nature if you stick to it. The student that learns this way – ultra-patient, some might think it – will perhaps proceed a shade slower at first but I have no doubt at all that they will learn the language a great deal more satisfactorily and satisfyingly in the end as a result. With specific respect to dictionary-use, I would advise learners only ever to use a dictionary to look up things they already know, either to check spelling or to find a word (in the language learnt) that is on the tip of the tongue or simply to satisfy your curiosity as to what the dictionary has to say about it. Never use a dictionary as a means of learning anything. It isn't any such thing.