1.•
In my opinion, … • I am of the opinion that…• I think that… • As for me • As far as I am concerned…• To my mind, … •I hold the view that • I would say that • From my point of view
2.• I feel … • Personally, I believe…• it seems to me that…• My impression is that • I have the feeling that • I have the impression that…
3• I am convinced that… • I am sure that • I dare say that
Note: you can use these expressions either to give your opinion(1), tell about your feelings(2) or even talk about your real conviction(3).