A first draft is about getting it written, not about getting it right. Don’t spend too much time on it
Think of an artist painting a picture – they get the basic outlines and then fill in the details later. That’s what a first draft should be – broad daubs of paint
Stories have a habit of hitting a wall as you write them. Don’t sit there sweating about how your hero will escape from the pit: just get on with writing the next part. A solution will occur to you eventually. It always does.
Don’t lose touch with your subconscious. If you can’t think of the right word, or phrase, or character, or description… miss it out! You can always add it in later.
Stephen King recommends finishing a first draft in a season (spring, summer…). Okay, that might not be possible for a part time writer, but even so, get it done as quickly as possible
Many writers find the first draft the painful part. The real pleasure of writing begins when you can take your time licking that first draft into shape…