Read or reread Deletion Policy especially Wikipedia:Deletion_policy#Reasons_for_deletion. Read WP:CSD carefully.

If you don't already have Twinkle running go to Preferences - Gadgets - Browsing - Twinkle (enable it here) then click Preferences to get to Wikipedia:Twinkle/Preferences <--or click this link.

Tick both boxes under PROD. Be sure the second box says PROD_log

Then under CSD tick all criteria boxes in the sections down to and including "Keep a log in userspace of all CSD nominations". Ensure the page name for the log is "CSD_log". DO NOT tick any boxes under "Do not create a userspace log entry when tagging with these criteria:" as that defeats the logging of CSDs you just turned on. Go forth and CSD junk.

Watch your own User:Username/CSD_log and User:Username/PROD_log to see how you are doing. Pages that don't turn red need followup. Maybe you were wrong and an Admin rejected the tag? Maybe the Admin was wrong. Maybe the page creator or someone else took the tag off. Maybe the pages need to be taken to MfD or AfD for discussion. Maybe the page was recreated by a spammer and should be deleted again.

• Stale Draftspace pages: Everything here User:MusikBot/StaleDrafts/Report is eligible for WP:G13 but you will find useful pages occasionally that should be promoted to mainspace (maybe with some fixes) or at least sent to AfC or deletion postponed.
• Category:G13 eligible AfC submissions mostly Stale Userspace AfC submissions. If the page is a sandbox with low value junk rather than something that should be removed completely you can just blank it instead of CSDing it.
• Category:Pending_AfC_submissions can be reviewed for SPAM and other Speedy Deletion worthy pages.
• Category:Declined_AfC_submissions is a good place to find G11 spam under various categories. Also look under blank submissions for pages that can be tagged WP:G2 test and at other categories for pages that should be removed. Clearing declined submissions has several benefits. It takes any pending ones out of the AfC backlog. It improves the average quality of the G13 list above making reviewing G13 candidates more interesting.
• Category:Stale userspace drafts includes all kinds of craziness that should be removed and a few gems that should be promoted. This is a bottomless well of pages but perhaps pick a letter and try to clear that letter over time. A good organized place to work on this is Wikipedia:WikiProject_Abandoned_Drafts/Stale_drafts
• Special:NewPagesFeed always needs attention.
• Use the search function to look for material that should be deleted across various spaces. For example "is a fag" on any Draft page might be a good search. "Groundbreaking" and "rising star" could be good phrases to identify promo pages. One editor has even been finding spam buried in CSS pages. Be creative with your searches and be amazed.

While doing cleanup always be alert for good pages that have potential. You can move mainspace worthy pages directly to mainspace, or submit them to AFC by adding {{submit}}

The experience and track record you build will prepare you for evaluating new pages at WP:AFC and WP:NPP