Make sure the directory that you choose to store the crawler in 'Basic Configuration' has recursive read+write access to your web-server.
While giving the directory paths in 'Basic Configuration', do not put '/' at the end.
Typical values for 'YouTube Setup' are already selected as the default.
What's the difference between 'once' and 'everytime'? 'Once' attributes are recorded only the first time when the video is encountered by the crawler. You want to do this for the attributes that don't change over the time, such as the title of a video. 'Everytime' attributes are recorded everytime the crawler visits a video. You want to do this for the attributes that keep changing, such as the number of videos for a video.
In 'Crawling Setup', use '*' as the value to ignore that parameter. For instance, if you want to run a process for every month of the year, put '*' in month. Once again, typical values are already given. Executing the queries and collecting 'once' attributes are scheduled to be executed at midnight (hour:0, min:0); collecting 'everytime' attributes are scheduled to be executed at 1am.