Reddit mentions of Anal Pleasure and Health

I can't believe no one has suggested this, but buy a dildo and practice with that first to get used to how it feels.

Here's a classic book on the subject:
https://www.amazon.com/Anal-Pleasure-Health-Morin-Ph-D-ebook/dp/B005HZ6FES/ref=sr_1_1?ie=UTF8&qid=1520622944&sr=8-1

Okay so I'm not a dude but I've basically made a life out of putting stuff in people's butts so I'm going to chime in like holy hell, haha. This is assuming you're a rank beginner -- if there's anything specific you're interested in, I can't promise I know everything but I do know a fair bit!

I wouldn't normally say this, but because you're young and I've heard so many horror stories from my male friends from your age range: please don't put anything in your butt that doesn't have a wide enough base to make sure you can get it back out again. Fingers are a great place to start, natch, but depending on how you're built, that might not be the easiest thing logistically. No carrots, no zucchini, no sharpies, no egg/bullet vibes even on a (very-easy-to-break) cord, no cheap cancer-causing jelly dildos that you bought on Groupon (these are all actual things that my male friends have admitted to having put in their asses and deep sigh don't do it). I've literally bought people sex toys before because they were too embarrassed because I don't give a shit, I just don't want them to get hurt. Good sex toys aren't cheap, but if it's going inside your body? Worth it.

Use a shitton of lube. Look for the ones marketed at gay men -- they tend to be the most useful. If you can use a silicone lube (because it's a steel plug or whatever), Gun Oil. If you're using a silicone toy on its own, Boy Butter or coconut oil. If you need water-based, Maximus or Hello Sailor have both worked well for me in the past (I abhor water-based lubes, personally, but sometimes you gotta), or the Sliquid Naturals hybrid is also good. Some folks swear by the powdered stuff (I think it's called J-lube?) but I used it a few times with a previous partner and had a heinous time getting the texture right and it didn't last.

If you're squicky or worried about mess and don't have ready access to laundry, gloves are your friend, as are chux/puppy pads (they're cheap, easy to buy, and then you just throw them away when you're done). Putting condoms on your toys also helps, but also, again, buy good silicone toys and then you can boil them, bleach them, or put them in the dishwasher (assuming you have one, and that doing so will not traumatize anyone you live with, haha).

you don't have to do a full enema every time you do anal play and in fact that can be really harmful in the long term. If you don't actively feel like you have to shit, aren't doing super-deep penetration and/or don't mind getting a little messy (it's an ass, these things happen), you'll be fine like 95% of the time.

Personally, my favorite plugs come from njoy (steel) and holy shit have I bought my share of those for people haha. Most people, I've found, have a preference between plugs and dildos -- you'll have to experiment some to figure out what does it for you. (Like... some people just want to be filled and left alone, hence the plugs, that's what feels good. Some folks love the sensation of being stretched open, so they're more into fucking -- I've had positive reports about the Tantus Silk line, which is designed specifically for beginners -- I own literally all of them and they're super smooth and don't have a defined head and it's great) If you have trouble getting things in there at first but it doesn't hurt, it just feels like you can't do it, then you might have better luck lowering yourself onto the toy instead of trying to push it inside yourself.

Just take your time and know that your body has an anatomical limit that's determined by a lot of factors, and very very few people can do the giant Bad Dragon shit that seems to be everywhere (I say this because I know a lot of men who are size queens and end up being horribly disappointed that they can "only" get up to a certain size of toy or a certain number of fingers). So if you get to a point where you just can't take anymore because it straight-up won't work, that's extremely normal and don't stress about it.

There's a book called Anal Pleasure and Health that I found extremely helpful when first doing butt stuff with other people.