Try thinking of the grammar structures like mathematical equations.
For example: ir + a + infinitive = to do something
An alternative to ordinary flashcards is a file folder flip chart.
1. Take 3×5 index cards and cut them in half (so there are 2 pieces of 2.5 x 3). Cut as many as you need
2. Tape the top of a card a tape it to the inside of the file folder.
3. Continue taping cards upward in a column, so that about 3/4 of an inch shows on the bottom of each card. You should be able to fit three columns of cards per side of the file folder.
4. On the 3/4 inch of free space of one card you can write a grammar structure, then flip the card over and write the English equivalent on the other side. Or write a verb on one side and the conjugations on the other.
5. You can color code the cards to coordinate with what kind of structure it is, red for -ar verbs, etc…

To remember the preterit endings I use the tune of the Mexican Hat Dance. Hable, Hablaste, Hablo, Hablamos, Hablaron

For the preterit ir/er verbs I use the tune of ‘row, row, row your boat’
Vivi, Viviste, Vivio, Vivimos, Vivieron, Comi, Comiste, Comio, Comimos, Comieron

My best advice would be to point out patterns that tend to occur in the language. Spanish is a very structured language (a lot less random than English).
For instance, the verbs are all -ar, -er, or -ir and tend to follow the same basic conjugation format with the exception of irregulars. I find that it helps to make up songs or rhymes involving the conjugations.
For flash cards, I’d try putting the form of a word/grammar rule on the front, and the answer on the back. Just keep reviewing them and you should get some results.