This is just a general comment to anyone reading this thread regarding my two posts about informal and formal speech in writing in Spanish specifically:
1/ There must be a distinction made between informal and formal address.
- formal letters have ud. forms and informal letters have tú forms and this must be maintained throughout the letter.
-if using the correct verb form presents difficulty the way to improve is via practice. Outside of the cultural nuances regarding when to use ud. or tú, one must know the difference for example between hablas/habla, caminas/camina, vas/va etc.
-a suggestion is to practice writing informal and formal letters in Spanish and give it to someone to correct. Of course a person who is in the capacity to do so and speaks well. The person correcting the letter should be able to identify crucial aspects of it that are important such as distinguishing between an informal and a formal letter, ensuring the verb forms are correct and consistent throughout, the correct tone etc. Practice will improve your writing skills and accepting the errors you make will enable you to be aware of your areas of improvement.
-after finishing the letter proofread it out loud. Highlight all the verbs and ensure that they are correct according to the type of letter it is- informal or formal.
-keep all the letters you write and look at the corrections before you write the next one and slowly and surely you will see improvement. Resisting to practice if this is your weakness in Spanish is equivalent to putting up your own barrier.
2/ Most dictionaries have sample letters in both Spanish and English. I suggest reading them as they provide a wide variety of scenarios and give you a great feel for the cultural nuances as well.
3/ Remember in Latin American the cultural norms do change and some countries are more formal than others. Colombia is a perfect example of ud. usage most of time vs.
tuteo countries (informal address most of the time) like the DR and
PR.
Here's a good link. Something to start with for Spanish:
Format and layout of a letter in Spanish.
-LDG.