I know, for myself, that when I detach from the outcome, I manifest things very easily. Often, I will think about something in passing and then a little while later ... *poof* ... there it is. One day, I had a bunch of random little things all manifesting one after the other in a very short space of time, and it really freaked me out. LOL
With things that I give more thought to, it does seem to take longer. I start to think about them more, and then I start fretting, and I can feel the resistance building. Focusing on what you want and practicing visualization and the like seems to work well for some people, but I subscribe to the 'ask and forget about it' theory. That works best for me.