I've been an admin for quite a few roleplays and I have also been a roleplayer looking through the tags for an rp; however, neither of those things make me an expert. Please take everything I say with a grain of salt. If you found this helpful please like or reblog.
Don't beg.
Your rp is killer, so have some self confidence. You can't expect someone to take pride in being in your rp if you act like you aren't proud of it. Confidence goes along way when it comes to getting interest in your rp.
Don't advertise certain faceclaims requested by a rper in the group.
From my personal experience I've found that the roleplayers of your group only request this because they are desperate for the ship. If someone sees this advertisement and joins the rp because of it, chances are they are going to only talk to one another which can cause cliquey-ness in your rp. I personally suggest posting the ask but simply not tagging it.
Don't forget to check your grammar/spelling.
It's unrealistic to expect you to get things right a hundred percent of the time, however make sure you read over every promo you post and check the spelling because this could turn off potential applicants.
Don't over queue.
What I mean is try not to flood the tags. It turns off potential applicants if you are all they see in the tags. Try to space out promotions and limit the amount you post a day. I would say twelve times a day for your queue over twenty four hours is a good amount.
Don't lose faith.
I understand that trying to get people to apply can be tedious and boring, regardless you have to keep your faith. You just have to find the right people to apply. It can take a long time for you to gain interest but as long as you are persistent and you keep faith, as well as hope, all should pan out.
Do follow your vision for the rp.
Tons of people have a million different ideas and they may suggest you to change things in your rp. It is good to listen to their suggestions but I'd say to take them all with a grain of salt. You'll never be able to please absolutely everyone so make sure you always get the final say, after all this is your rp.
Do advertise your greatest strengths.
Be humble but let others know that you have got a great rp to offer. Most commonly I see roleplays advertising what the admin is doing at the moment in their life or saying what faceclaims they have open. I'm not saying either of the two or wrong but I think the greatest way to gain interest is advertise what your rp is about. Do you have an interesting plot? Advertise it. I know I'm always looking for a unique rp to join. Don't be afraid to say what you have to offer.
Do utilize all the services rph blogs offer.
Shoutouts are the most common utilized source that a rp help blog offers but there are so many other great things that you can use to advertise your rp. Don't limit yourself to just shoutouts. Try asking for opinions, reviews, submitting a promo, etc.
Do use scheduled posts.
You can use scheduled posts to set a time and day for your post to, well, post itself. This is great to use for an admin or admins who are on a lot. That way when you are advertising on the main you don't have to worry about your main and your promo blog storming the tags. Set scheduled posts to when you know you won't be on so even when you aren't on you can still be gaining interest in your rp.
Do get second opinions.
I suggest asking for opinions because the person may catch something that you haven't noticed. I think they are a great source to help gain interest in your rp. Think of it as getting a poll for what the public would want to see in order for them to apply.