In literatures, I often come across interactions like the $D^*D\gamma$ vertex:

$$\mathcal{L}_{D^*D\gamma}(x)=\frac{e}{4} \epsilon^{\mu \nu \alpha \beta} F_{\mu \nu}(x)\left({g_1} D^{*-}_{\alpha \beta}(x)D^+(x)+g_2 \bar{D}^{*0}_{\alpha\beta}(x)D^0{x}\right)+h.c.$$

where $D^{(*)}$ stands for $D^{(*)} $meson.

I can only check that each term respect parity, however why the relative sign between $g_1$ and $g_2$ are positive? Is it just a convention?

The above formula is about pseudo-scalar vector (massless) vector or $PVV$interaction.

As to construct $VVV, VPV$ or other fancy interactions, I have no idea.

I've searched on the web and the textbook, but they are not focused on this.

So how to construct interactions like this from scratch?

I'll be very appreciated if someone could tell me any books or references on this topic.