1. Figure out what equity you would have wanted if the company already had raised a round
2. Adjust for anticipated dilution of the Series A round.
3. Then, either double or triple that adjusted number to account for pre-funding risk, depending on how far along you are in the bootstrapped phase.

If the company does not intend on raising capital then skip 2.

I would say you should be in 3%-6% range if you are working strictly on equity. The norm is a 4 year vest with 1 year cliff.

You can shoot me message and we can discuss.