(Looking over the other answers that have been submitted, I see that most of this has already been covered there. Still, there may be some value here, since I've included attestations.)
1. The man is like a dog.
For a simple statement of similarity, of the sort 'x is like y,' I think the best approach is to use the adjective similis + dative, as in Pliny the Younger, Epistulae 8.21.5:
delicatus ac similis ignoto est, qui amici librum bonum mauult audire quam facere.
He is self-indulgent and like an ignoramus, who would rather listen to the good book of a friend than help produce it.
This would give Homo similis cani est.
For more complex statements of similarity, where you're saying, not simply 'x is like y,' but 'x does y like (i.e., in just the same way as/in the manner of) z,' an adverb like velut(i) can be used. An example is found in the opening of Sallust's Bellum Catilinae (1.1):
omneis homines, qui sese student praestare ceteris animalibus, summa ope niti decet, ne vitam silentio transeant veluti pecora, quae natura prona atque ventri oboedientia finxit.
All men who are eager to surpass all other animals should try with all their might not to pass their life in obscurity like cattle, which nature has fashioned face-down and slaves to their stomach.
Additionally, because Latin adjectives in the nominative (and also accusative) are often used where English prefers an adverb, similis can also be used for these statements, as in Pliny, Epistulae 8.14.24:
sed quid ego similis docenti? cum discere uelim, an sententias diuidi an iri in singulas oportuerit.
But why do I speak/write like someone giving a lesson, when what I want is to learn whether it was fitting that the proposals be divided or taken on individually?
2. We go many places, such as the forum.
One way to give examples that involve single words or phrases (as opposed to clauses), is once again to use velut(i), as in Quintilian, Institutio oratoria 2.21.8:
sed neque infinita est, etiamsi est multiplex, et aliae quoque artes minores habent multiplicem materiam, uelut architectonice (namque ea in omnibus quae sunt aedificio utilia uersatur) et caelatura, quae auro argento aere ferro opera efficit.
...and other lesser arts also have varied material, such as architecture...and engraving....
This would give In multa loca imus, velut (in) forum.