Summarize:

It's common for English speakers to see Latin words and phrases italicized, such as in medias res ("in the middle of things") or in loco parentis ("in the place of a parent"). However, Latin words and phrases that have entered common usage are usually not italicized -- including i.e. and e.g. To indicate a separate clause, you can either insert a comma before "i.e." or "e.g." or you can use parentheses, both of which are shown in the examples above. If you use parentheses, open them right before the "e.g." or "i.e." and close them after you have given your example or alternate definition. For American English usage, you should always put a comma right after both "i.e." and "e.g." as shown in the examples above. For British English usage, do not put a comma right after either "i.e." or "e.g." If you're just writing for yourself or in an informal situation, you may not have any specific requirements. However, if you're writing in a particular academic discipline, or in a particular profession (such as journalism), you will probably be asked to write in accordance with the relevant style manual. For example, APA Style, the official style of the American Psychological Association, is used widely in the social sciences and in professions like journalism. APA states that you should always put a comma after e.g. and i.e. when using them: "Some sources (e.g., Janet, 2010; Jeff, 2015) argue that mushrooms are tasty" and "There are three meals in the day (i.e., breakfast, lunch, and dinner)". If you use a sentence that includes i.e. and a parenthetical comment, make sure that the restatement is directly equivalent to what you said first: you should be able to swap them out without a loss of meaning. The sentence "His favorite type of sandwich is an open-faced sandwich (i.e., one that uses only one piece of bread rather than two)" represents correct usage of i.e. The sentence "His favorite type of sandwich is an open-faced sandwich (i.e., a panini or similar type of sandwich)" represents incorrect usage, because "a panini or similar type of sandwich" is NOT directly equivalent to "an open-faced sandwich." If it sounds reasonable, then you are probably using the right one. For example, "I like quiet activities (e.g., reading)" becomes "I like quiet activities (for example, reading)". When trying this with i.e., it is often easier to use "in other words" instead of "that is."
Italicize only if specifically asked. Use parentheses or commas with both. Determine any style manual requirements. Ensure that what you write after i.e. means the same as what precedes it. Try replacing the abbreviations with their meaning.