Selection on income tax return form ITR is decided by the following two factors -
How much is the share of income under a particular head, if there are more than one head of income and How one want to treat that income.
In your case, if the income as vocational trainer is one time and/or casual in nature (some time it may be there and some time it may not be there) then it needs to be considered as income from other sources and ITR1/2 shall be most suitable.
However, if the income as vocational trainer is going to be substantial, every year and year after year, if it's regular in nature then such income shall fall under income from business and Profession and ITR 4 shall be suitable.
So, from this year and thereafter if every year you will going to receive this income than, You can file return in ITR 4 as prespative Taxation.