To think is one of the most popular ways to express your considerations as well there’re some useful synonyms which can make your speech brighter:
Verbs: to consider, to believe, to suppose, to count, to deem, to reckon, to judge.
Expressions: in one’s view, in one’s opinion, to one’s mind, to one’s thinking, from one’s point of view.
PS. Definitons and other interesting information regarding to think you may find here:http://dictionary.reference.com/browse/think