There are many ways to do camel-case. When given the choice, I use the following rules, because they are simple and easy to follow and don't require any exceptions to be made for certain words.

UpperCamelCase

e.g. for type names or other cases where you want the first letter capitalized.

Upper-case the first letter of each word, then smash the words together.

Examples:

• "party sauce" becomes "PartySauce"
• "XML decoder" becomes "XMLDecoder"
• "XML HTTP request" becomes "XMLHTTPRequest"
• "I need a new ID card" becomes "INeedANewIDCard"

lowerCamelCase

Ususally used for variables and property names

Lower-case all words completely, upper-case the first letter of each exept the first, then smash the words together.

Examples:

• "party sauce" becomes "partySauce"
• "XML decoder" becomes "xmlDecoder"
• "XML HTTP request" becomes "xmlHttpRequest"
• "I need a new ID card" becomes "iNeedANewIdCard"

Why?

I've seen other conventions that are less self-consistent or give bad results.

For example:

• lowerCamelCasing by lower-casing the first letter of the first word without lower-casing all words results in things like "xMLHTTPRequest", which bothers me.
• lowerCamelCasing by lower-casing the entire first word can results in things like "xmlHTTPRequest", which also bothers me.
• In either upper or lower-camelcase, some codebases arbitrarily allow certain words to keep their original case while others are subject to the usual rules. Javascript's "XMLHttpRequest" being a well-known example. But "ID" tends to get special treatment, too. This just makes it harder to follow a convention because a list of exceptions needs to be referenced.
• Allowing words under a certain length (such as 3 characters) to keep their original casing, but transforming others. Similar to the previous case, why add unnecessary exceptions?

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