How can i check for post_types in the templates?

To check if it’s a page:

Function Reference/is page

To check if it’s a single post:

Function Reference/is single

To check for a custom post type, it can depend on when and where you want to check. For example, if your in the loop, you could do something like this:

if ( 'my_post_type' == get_post_type() ) {
    /* Stuffs */
} else {
    /* Other stuffs */
}

Function Reference/get post type

You can also make specific single and archive template files that target a specific post type. You check out this page for more information on that:

Template Hierarchy