I have a couple of different ways that I handle this.
Scenario 1) a lot of times people aren't really serious and they just throw it out there as a compliment "damn Alex, are you on steroids? you got big!!" like if it's a friend's mom or sister or something. For that I just take the compliment, laugh with it and the whole thing moves on. non issue
Scenario 2) other times I'll be out or at work or something and some jealous dude will blatantly ask me accusingly if I'm on something. I'm the kind of guy that has no problem not talking to people I don't like so basically I just tell them no in the appropriate way and blow them off. They already know they're being rude in the first place so they're usually not going to step over the line again. I do however have some guys at the club (I'm a bouncer), like other bouncers that won't let go and it comes up every once and a while but the thing to keep in mind is that no one will really KNOW you're on gear until you tell them...so as long as you keep denying it without looking like you're trying too hard to prove a point, they just look like rude people that are jealous of you. And I emphasize that point. NEVER look like you need to prove that you're natural. Just treat people like assholes that are being assholes- because let's face it, that's what they are for coming at you like that, answer no if you have to, and ignore them and treat them like they're not worth your time. This strategy works really well for me.
Scenario 3) Sometimes people aren't being jerks. It's people that you consider good acquaintances or friends and they just really want to know how they can get some gains. For them, I just tell them that I picked up some tren xtreme and novedex from max muscle (you can tell them whatever prohormone is available to them in your area or online like superdrol or phera plex).
So basically that's what works for me. And it works REALLY well. I've done about 4 cycles now so it's pretty damn obvious but it hasn't been a problem at all for me. I'm sure that if I came out and said that I was on juice a lot of people would be like, "I knew it!!" but none of them really KNOW. They just suspect it and it's like 50/50 in their heads or whatever and it doesn't really matter as long as I just deny it and I'm convincing enough. It never comes up a second time. Even with girlfriends and exes and people that I spend a lot of time with.
I hope that helps. Good luck with your first cycle bro. Remember to hit 4000 calories and 300 grams of protein ed and have an ai or serm handy in case if your nipples tingle!