  Let $X$ be the blow up of $\mathbb{P}^2$ at $r$ general points
$p_1,\ldots,p_r \in \mathbb{P}^2$. We study line bundles on $X$ given by plane
curves of degree $d$ passing through $p_i$ with multiplicity $m_i$. We
establish conditions for ampleness, very ampleness and global generation of
such line bundles.
