Le petit Robert a ma préférence pour refléter et définir le français contemporain, par son amour des mots, plus que des définitions.

Les définitions sont adaptées aux mots : tous ont leur transcription phonétique, certains ont leur histoire, les idées associées, les synonymes ou contraires, les variations.

Plus qu’un distributeur de définitions, il permet d’abord d’appréhender un mot tant par l’intuition que l’on peut en avoir selon l’environnement dans lequel ils évolue, que par les définitions et citations elles-mêmes.

Pour formuler une phrase de qualité, il permet de varier ou de préciser son vocabulaire pour la bonne expression des idées.

C’est plutôt un dictionnaire littéraire, qui ne référence pas forcément tous les termes techniques, scientifiques, médicaux que l’on peut trouver dans Le petit Larousse, mais, à mon goût, c’est le plus francophone.

De plus il donne les conjugaisons, et annexe les datations principales des mots, et les noms et adjectifs relatifs aux personnes et au lieux.

… et c’est grâce à lui que j’ai pu répondre judicieusement quelquefois sur ce site.

You have the choice between the rival compact dictionaries Petit Larousse and Petit Robert. I prefer the Petit Larousse since it is far more precise, and its famous “pink pages” contain common expressions, Latin phrases used in French, proverbs etc. Both Larousse and Robert have good conjugation and grammar sections.

However, my preferred dictionaries are:

• The Hachette Encyclopédique which is a little bigger (although there is a very practical pocket edition I used in highschool). It contains a lot of encyclopedic information about places, people, cities, etc and also has good conjugation and grammar sections. It is widey used by cruciverbalists, arrowords enthusiasts or Scrabble players.
• The Petit Larousse
• The Littré is a normative dictionary that gives a lot of information about the words themselves. It might too advanced for you (and it is difficult to find a good modern edition), but if you see it in a library while looking for advanced information it can be really useful.
• The Bled / Bénac grammar guide is a small (pocket-size) book that contains every complicated rule of the French language. It is not a dictionary, but it is of great value each time you forget a rule or its exceptions, or if you don’t know which tense to use. Bled was born in 1899 and wrote so many grammar books and exercise books for schools that nowadays a lot of books written in his particular style are called “Bled”.
• The Larousse du XXème siècle is an old (1920-1927) dictionary in 6 books that had a great success. You might find it in some libraries. It is not modern, but when you need a very precise definition of an old word (example, an old tool or architecture style) it’s very good.

Although I recommend the Hachette, I agree with cl-r’s answer. The Robert is a good learner dictionary and well suited for an everyday use, even if I was sometimes disappointed by its lack of precision for such a big dictionary.