With talking, it's not as easy as with writing.
With writing, you need to read over what you've written, and try to pretend you have never seen the sentences before. Pretend you are someone else. Ask yourself what another person would understand from your words. If that is different from what you meant, then you need to change it.
In speaking, you could ask the hearer to paraphrase back to you what you said. If it's not what you meant, you should try to rephrase it until the person understands the exact message that you intend. You'll need to find someone with patience to do this with though!
Of course, you can also write short passages and post them here, and ask whether they sound logical, and if not, what errors you've made.