I like Lucas but whereas he has flattered to decieve a little, Babel has grown into the team. It's probably no coincidence (and I think perhaps even the "pro's" would accept this) that Babel is the one out of the two who has been given a regular starting berth in the team, but only the Brazillians biggest and most deluded fans would argue that he is currently good enough for a starting spot on merit.
So anyway what of Babel? Well many people have alluded to the fact he doesn't use his left foot that much, but I shouldn't think that unless he intends being a left-winger all his life it would be too much of a problem. I've seen him shoot and cross with his left foot with varying degrees of success so I wouldn't count it as a particular weakness. He does seem to posess a good hit when he just unloads, obviously has a tonne of pace (which he doesn't seem to know how best to use on occasions) and has a trick or two to take him back onto his favoured right side when the situation allows. I haven't really seen him head it much that I can remember but he would probably have the athleticism to be a good header, if not the inclination.
I think he can improve most in how he uses himself, where he puts himself during a game and his general decision making in posession. To me whether he starts on the left side, right side or as a conventional front man, he should be encouraged to track in off the touchline more and make an angle for the full back. Upon recieving the ball, he kind of needs to think less if that doesn't sound too odd. He's fairly obviously a nightmare to defend against when he's actually in full flight with the football at his feet, as he asks defenders to make decisions with critical outcomes very quickly and with tiny margins for error. There won't be many who will shepherd Babel down the outside because like a young Henri he has enough after burners to go through the gears and simply go round the long way. So nine times out of ten it's a stand and deliver situation for a defender if Babels in full flight, they're either having him over or they're tackling him cleanly, and it happens in the blink of an eye.
His gameplan should therefore be all about getting in full flight with the football at his feet as often as possible. Surprisingly it's not quite as simple as just "get the ball and run with it FFS!!" as there are a couple of factors. Firstly, as he is reluctant to track in off the touchline (or he gets coached to stay out there but I think that's unlikely TBH) it's sometimes difficult firstly to get the ball to him, and secondly he's often got nowhere to go when he gets it. At the moment the full back is happy to ease him infield where he gets confronted by the central midfielders and he nine times out of ten gets rid of the ball.
Well the first bit is quite easy to fix, and this really is as simple as saying "just come in off the touchline by ten yards when the fullback gets it FFS!!"

One last thing, they need to work on a few patterns which allow him to actually recieve it when he is in or somewhere near to full flight. I'd be very comfortable as a defender if as currently happens he almost always recieves the ball standing still, whereas I'd get very nervous about him getting the ball on the move. Him doing so got us the penalty which beat Arsenal in the Champions league.