Being a sparrer, I can get a few sparrers to join me and we raid bases. Then you will run into random people that are just pking as Nicholas said above. Recruit any pker you see and pm them saying "Do you want to base". Because then they will know why you want to recruit them and then they will decide rather than looking at a random recruit not knowing what you want from them. I'm not saying you have to do this but it is more effective. Plus, when you recruit people, make sure you can start basing within at least 5 to 10 minutes or you will see members getting bored and start to leave. So recruit a few pkers you see, then start basing fast.
Tips:
-Know what base you are going to raid prior to the raid.
-Make sure you have at least 2 or 3 people that know what they are doing or have some sort of basing skill. I'd recommend looking at their kills or their gun. People that look pretty good.
-If someone asks to join, ask for what they have for gun
AND melee. Bold for and because a melee is very important when it comes to basing since it is the best way to take the flag. So if they don't have a decent melee, don't recruit them UNLESS they have a good gun. They might not be that skilled at basing, but a good gun is decent.
-It doesn't hurt to ask a pro to base with you. Just go for it and you never know if they might join.
-Do not recruit ranked or high basing our gang members. If they have a tag such as Obsidian, NBK, M2S, etc. they most likely will not join.
-Give some people recruit powers and tell them specifically what kind of players to recruit. This helps a lot because you can get members faster other than you scrambling to find people by yourself.
Well anyways these are some tips. Good luck!