From my experience there is no need to pre-plan anything - there are a lot of guys available for free and a small fee on Grindr. Having said that, I've made a few contacts on x.com that I would like to meet when I am in Manila next. I've never used a massage service, but I find the guys on x and Grindr are more to my taste.
When it comes to price I would always overpay, regardless of the agreed price. Even if you meet a young guy who isn't after money, a couple of thousand pesos can really help them out.