can you explain more about what you want to achieve ?

For security reasons I want to change my 'wp-admin' folder to 'admin' and 'wp-content' to 'content' and 'wp-includes' to 'includes'.

I would advise not primarily because of the number of references made by wordpress to those directories. Even if you search and replace the references and rename the folders, your Wordpress updates using the automatic updater may fail and then you'll have security breaches unless you manually update the installation by uploading the files every time a patch is released.

This thread touches on it,
But there are many ways to accomplish what you probably want to do. What are you looking to do specifically?

I would like to make it so the wp- doesn't show up when someone views the page source. @Workman What are some of the ways to remove the wp-?

I see -- the methods I was thinking about were primarily focused on redirects so that the admin url was easier to remember.

You want to completely mask the fact that the site is using Wordpress though. You may rename the folders, but be prepared to search and replace all references of "wp-" in a fresh copy of Wordpress. I promise it will be a pain to maintain and update since updates overwrite same-named files in the web root, wp-includes,wp-admin, and parts of the wp-content directory, but you'll achieve it that way. As far as I am aware, there are not any plugins that accomplish what you want to do -- yet, but I'll double check.

My advice is to not rename those folders though. I understand wanting the look of professionalism, but these days Wordpress is seen more as a site framework. Even some news companies use a stock Wordpress install for rapid deployment and security and create plugins for all the features they want.

Slightly easier (but messier in your web directory) and achieve the same result is to move the images/javascripts/etc into your webroot. So instead of storing those sorts of files in:
/wp-content/themes/mytheme/js/javascript.js You could move it to:
/js/javascript.js
and change your theme to reflect those paths -- same for uploaded content.

It's not ideal, but it will accomplish at least some part of your goal.

@Workman Thanks. Have you seen a desktop program that can do a find an replace for search for php files? That should make it quicker.

Okay I think you can do it when you upload wordpress to your host using ftp change the wp- dir names and do remember that you have to change all the links in index.php file containing wp- and all files which include some other files from any of the wp- folder.
But you have to remember that after that you cannot automatically install plugin and wordpress themes and you have to do all those things manually.
even you have to update your wordpress manually.
Its very time consuming task.