Writing a coherent letter takes a lot of practice. What steps could one use in writing to form a coherent letter in german?
A German letter is not much different from a letter in any other language. The first thing to be aware of is whether it is in an official context or in a private context.
For example if you are writing a letter of application where you don't know the person that might read your letter you might want to start your letter in a formal way, similar to the english version "Dear Sir or Madam," you could write
Sehr geehrte Damen und Herren,
As you can see the biggest difference between the common phrase when comparing the languages English and German is that the English version uses the male noun first, while in German you would first address women. Another difference is that the Englsih version uses singular and the German version uses plural when not knowing who will be the recipient - in English you would address the single reader, while in German you would address some sort of audience, like a crowd.
If on the other hand you already know the name of the person that will receive your letter you write something like
Sehr geehrte Frau Schmidt,
Sehr geehrter Herr Schmidt,
In a private context, such as when writing a letter to an old friend, you want to write something more casual, such as "Hello Martin, " which would be translated to "Hallo Martin," (not a big difference here between the two languages). Depending on the way you communicate with your friends you could of course also simply say "Hi Martin!", which would work in both languages.
There are lots of resources on the internet that show you how you can write a letter. For example this website gives you an overview of writing an official letter ("Einen offiziellen Brief schreiben - Inhalt und Tipps" = "Writing an official letter - content and tips"). The same site also has tips on writing a personal letter here ("Einen persönlichen Brief schreiben" = "Writing a personal letter").
In general a letter consists of the following things:
- header - this includes things like the address of your recipient and your own address, the date, telephone number or e-mail address; in case of a personal letter the date is often enough as the addresses are already written on the envelope and not necessarily repeated
- subject - sometimes this is used to write a little summary of the letter; I've rarely seen this being used in practice; don't use this in a personal letter
- salutation - see my examples above
- content - this is the main part of your letter
- closing - there are a few common phrases, similar to how in English you would write "Yours Sincerely" or "Yours Faithfully" depending on whether you know the name of the receiving person or not; in german you could simply write "Mit freundlichen Grüßen" ("With kind regards") or "Viele Grüße" ("Many regards") or in a very official setting something like "Ich freue mich auf Ihre Antwort und verbleibe mit freundlichen Grüßen" ("I am looking forward to your reply and remain with kind regards")
- signature - your personal handwritten signature
- attachments - in case you have any documents that need to be attached, such as a Lebenslauf ("CV")
Writing the content in a coherent way is something that has nothing to do with the German language. In a letter you start with detailing the situation and then giving your main points that you want to bring across to move to some sort of closing about what the next steps should be.
For example in an official setting you could establish where you have seen advertisements, such as whether you learned about a company through a news magazine or a website, and in a personal setting you can mention what triggered you writing to your friend.
You would then move to the main points, such as explaining why you want to apply for a certain position or what you want to tell your friend.
In the end you would detail that you hope to continue a partnership with a business partner, are looking forward to a reply about whether there could be a job interview or that you simply hope your friend is having a good time at home while you are spending your vacation in the sun.
This website can give you a step-by-step introduction into writing a letter, from giving you an idea of where to put the address on the envelope over questions you should ask yourself about the recipient and yourself, over common phrases for things like expressing condolence and using a PS (Post Scriptum - an addition in case you have forgotten something in your letter and don't want to rewrite the whole handwritten thing; you shouldn't use this in an official setting and certainly not with a digital letter).