You'll notice in the lists below that many Alexa skills are called by using trigger words like open, start, play and ask. While select skills require you to use specific terms, others consider them to be interchangeable and will work with some or all of these phrases. Over time you'll begin launching your favorite skills by the words you feel most comfortable using. Initially, though, it can be fun to play around with each.
For tracking your food, you can use the Track by Nutritionix skill, which lets you record your food intake using your voice, or ask for caloric values of foods. (Alexa does the latter by default.) Say things like, "Alexa, tell Food Tracker to log a cup of almond milk" or "Alexa, ask Food Tracker how many calories are in two eggs and three slices of bacon."
The Capital One skill allows you to check your credit card balance or make a payment when one is due. This is secure: The skill performs security checks and requires you sign in using your username and password. Then, when you open the skill, you must provide a four-digit code to confirm your identity. Just be wary of who is around when using the skill -- anyone who overhears you say your personal key can access your banking or credit card info just by asking Alexa.
For tracking your food, you can use the Track by Nutritionix skill, which lets you record your food intake using your voice, or ask for caloric values of foods. (Alexa does the latter by default.) Say things like, "Alexa, tell Food Tracker to log a cup of almond milk" or "Alexa, ask Food Tracker how many calories are in two eggs and three slices of bacon."