Perhaps most algebraically natural is to go from right to left. We have $$\frac{\sin\theta+\cos\theta}{\sin\theta\cos\theta}=\frac{\sin\theta}{\sin\theta\cos\theta}+\frac{\cos\theta}{\sin\theta\cos\theta}=\frac{1}{\cos\theta}+\frac{1}{\sin\theta}=\sec\theta+\csc\theta.$$
However, going from left to right is also in a certain sense natural. Express the left side in terms of sines and cosines. We have $$\csc\theta+\sec\theta=\frac{1}{\sin\theta}+\frac{1}{\cos\theta}.$$ Now bring the expression on the right to a common denominator $\sin\theta\cos\theta$.