Maybe the situation is different elsewhere but at the 'Mate, at least afternoons, I find that there are still a number of dancers who will make a 'cold approach', that is, they will come to the table without any 'prompting' on my part. On some days, there can be almost too much of this, but I find the more experienced girls will sometimes open the conversation by asking "Are you waiting for someone?" and this allows one to politely avoid having the girl sit down at one's table.
In general, I would say that it's fairly easy to get a dancer to approach by watching her and smiling a bit - in most cases she will take the hint and drop over. This may take a while if she is engaging with her smartphone, but if you are in a hurry I guess the direct approach (walk up to her) is recommended. I certainly understand that not everyone has the same view on this matter. Some may prefer the girls to approach, but if a lot do, this can be problematic - if other dancers note that a gent is chatting for a minute or so with a succession of ladies but never going to the CR, they may begin to avoid him as not having CR potential.
My own preference is that dancers will be keeping an eye out (even as they use the smartphone and chat with other girls) so that one can give an indication of interest and then have them approach. On the other hand, I have no problem taking a more direct approach if that seems to be required. Certainly, I will never approach a dancer while she's chatting with someone else.
A number of posters over the years have noted that the dancers at the 'Mate do not circulate that much and maybe this has some validity. It may be that a number of the girls are on the lookout for their 'regulars' and are less inclined to make an unprompted approach.