Some of the letters of the Rashi script are easily confused with the standard letters you have already studied. I will poiint out the most obvious differences between the letters that seem most similar.
Aleph and Chet
The two most easily confused letters are Aleph and Chet. Notice that with Aleph, there is an extra ascender that is not found in the Chet:
Tet and Ayin
Notice the direction of the lines for Tet and Ayin. With Tet, the second stroke is nearly vertical, whereas with Ayin the second stroke runs into the first stroke:
Lamed and Tsade
Another set of easily confused letters are Lamed and Tsade. To differentiate them, be careful to note the direction of the ascender for each letter:
Mem Sofit and Samech
Another set of easily confused letters are Mem Sofit and Samech. These are especially difficult to catch since some Hebrew typefaces make the Mem to look like a Samech. In addition, Samech looks like Mem Sofit in script!