How do you buy language services?

Language services include foreign language teaching, non-official or official translation, proofreading of the translated text, its localization in the local language version, various types of interpreting, exam-specific preparation for international tests in a foreign language, etc. 
When purchasing language services, if you haven't done so already, you may "feel dizzy" from all the offers found on the internet. How to choose depends on the specific needs of an individual client. 
1. If your priority is TIME: the obsolete practice of many language service providers is charging a speed surcharge. Look for a provider who is willing to make a translation ASAP at a standard, market price. For example, the price of official translations in Slovakia is set outin the Decree491/2004 https://www.zakonypreludi.sk/zz/2004-491 It should be borne in mind that the law allows, but does not mandate, a speed surcharge. 
2. If your priority is QUALITY: if the translator or the agency ask for a surcharge on the grounds of a "field-specific / expert" text, that is a red flag. We, translators, only translate highly specialised texts. An experienced translator works in CAT software (computer-aided translation), makes use of extensive terminology databases and has external consultants available to assist him or invites you to participate in the final version of the translation through your expert interventions into the translator's draft version. 
3. If your priority is MONEY: the good old saying "I am not so rich as to afford cheap services" applies here unless, of course, the text is of a standardized nature (think birth certificate).