Hi, I enjoy writing film reviews too and there is a basic format to follow:
1)Title- Make it catchy. Play with the film title or maybe give clues as to whether you enjoyed the film or not. I did not enjoy Dinner for Schmucks so I wrote a review titled Dinner for Schmucks is Not on the Menu.
2) Make the opening paragraph a general summary of the film and give early indications on your overall impression of the film.
3)You can use the following paragraph to continue the summary, but don't give away the ending!!!
4) What did you like about the film, looking at the plot, the characters, the dialogue, the setting, the music, the list is exhaustive but be descriptive. Remember there are usually some positives in a film unless it is a complete turkey.
5) Now the negatives- but give good reasons. Was it cliched?
Was the plot weak? Was the continuity terrible?
6)Talk about the characters and how the actors portrayed them. Could you identify with them? Did you care about them? You can mention also the direction of the film, this will prove you really know your stuff.
7) Resummarize briefly. This is the make or break of whether you have inspired a reader to either see the film or give it a big fat miss. It could be that it was a sci-fi film and that is not your bag, but don't slate it for that reason alone. Bear in mind that someone out there would embrace it, so say who it would may be appeal to. As a final point you could may be even score the film star ratings.
Ultimately though it is your use of the English language that will win the day.