It must be remembered that the French are used to hearing their language mangled. The English live just across the Channel, and now that they are both part of the European Union the English are busy going across there to buy cheap wine, and expounding in broken French on how the Brittish saved the French in World War II. This is all of course rot, as we know it was the Australians who did all the work, and many visitors from this country arrive in France to tell people of this. Unfortunately, the Australian mouth is too lazy to open itself more than a couple of millimeters, let alone master some of the more tricky vowel sounds and nasals.
If this doesn't persuade you that there are hordes of people currently massacring the French language in Paris, one need only be reminded that the Americans are worse. I am not sure of the quality of French produced by non-Anglophones, but the Italians seem to fit in very well. There is an annual pilgrimage of dirty old men from Italy to Paris. If a female is pinched on the backside in Paris, it is most likely that it was done by a tourist, but still many women return complaining that the French are all perverts. Please note that most French perverts visit Scandinavia or Germany.
The point is that if you go to France with an awful accent, the French will just pretend that they can't understand you. Far better to have somebodies undivided attention when you tell them what a prat they are. If you follow the guidelines given below and still find it difficult to affect a French accent, try the following rules of thumb:
ll: Most phrase books tell you to go into far more detail than is necessary here. It is pronounced by the French as the "y" in "yacht", not some bizarre "ly" sound. It used to be done that way, but it was too much trouble even for the French.
j: Spelt by linguists "zh", the French pronounce their j's as we pronounce the "s" in "Asian".
eu: A pretty revolting sound that is a shortened version of "er" in "her", without the rolling r.